Aerial Photography Images Research Articles

Mapa de zonificación de amenazas por inundación del casco urbano del municipio de Quibdó (Chocó): Estudio basado en la interpretación de imágenes de radar, de satélite y fotografías aéreas

A zoning map of areas which flood due to the Atrato River and its tributaries (the Cabi, Carano and Yesca) over-flowing in the urban area of Choco (Quibdo) was drawn up to be used by aid authorities and Quibdo city as a planning and control tool. This research relied on CIAF (Centro Interamericano de Fotointerpretacion) support and assessment. This entity is a subsidiary institution of the Instituto Geografico Agustin Codazzi which provided their installations and the required geographical material. This research was initially based on interpreting radar (INTERA), satellite (LANDSAT) and aerial photographic images; this was verified by field verification of the in-terpreted data. Other variables such as climatic, geological, temperature, topographic conditions, historic and hydrological series and facts regarding the region were studied as additional information required for drawing conclusions. Aerial photographs provided the most reliable images due to their scales, quantity and quality and the date of when they were taken. Radar images (INTERA) were also important when visually analysing a sector’s topography as they were produced by an active microwave sensor (totally eliminating climatic obstacles). On the contrary, satellite images did not have great relevance due to the amount of clouds hampering any kind of analysis. Complementing these results, a calibration curve for analysing this section’s maximum flow values was based on historical series data regarding the Atrato River’s flows and maximum levels recorded at the Quibdo hydrographical station and the river-bed’s cross-section. Implications that the river would overflow or has over-flowed were statistically estimated on these results, thereby setting the limits (supported by cartographic data) for the corresponding areas at risk of flooding. A map marking areas at risk of flooding in the urban zone of Quibdo was then designed and a document prepared concluding that neighbourhoods on land lying at 25-27 metres above sea-level (or less) and located near the banks of the Atrato river and its tributaries are considered as being mid- high-flood threat areas, having 5-20 and 50-100 year return periods, respectively.

Analysis of sand dunes to determine wind direction and detect sand source sites (case study: Khartooran Erg, Iran)

Wind regime and sand grain size are two of the factors that determine the morphology and dynamics of sand dunes in desert areas. Regarding the importance of wind effects on sand dunes especially in Iran, in this study, Khartooran Erg was analyzed to determine wind direction and to detect sand source sites. Khartooran Erg is located on eastern north of Iran and lies in Khorasan Razavi and Semnan provinces. The area of Erg was determined based on geological and topographical maps and satellite images. Then, sand dunes of erg were classified, based on aerial photograph and satellite image interpretation. Sand dune forms in the Khartooran Erg are often barchans and combination of barchanic ridges, but there are also complex types of linear sand dunes. Based on field survey findings, the stabilized in the southern part of the Erg were separated, because of these sand dunes having been deformed. According to the presented models relationship between morphology and wind direction, the sand dunes were analyzed. The studies have shown that wind prevailing direction is eastern-north to western-south, the strong wind being in north-south direction. It can also be said that sand dunes which are located in the adjacent of Erg and are simple and separate can be used as the most suitable criteria to determine predominant wind. Also, regarding the Erg location with respect to upper plains and determined wind direction, it can be noted that sand sources mostly come from silt-clay flats of ending parts of Sabzevar Kal River rather than Jajarm Kal River.

Tectonic evolution of the central-eastern sector of Trans Mexican Volcanic Belt and its influence on the eruptive history of the Nevado de Toluca volcano (Mexico)

The Nevado de Toluca is an andesitic to dacitic stratovolcano of Late Pliocene–Holocene age located within the central and eastern sectors of the Trans Mexican Volcanic Belt. Morphostructural analysis, aerial photograph and satellite image interpretation, structural analysis and geological fieldwork were methods used to investigate the relationship between the evolution of the volcano and the tectonic framework of its basement. The study revealed that the area of Nevado de Toluca is affected by three main fault systems that intersect close to the volcanic edifice. These are from oldest to youngest, the Taxco–Querétaro, San Antonio and Tenango fault systems. The NNW–SSE Taxco–Querétaro fault system was active in the area since Early Miocene, and is characterized by right-lateral transtensive movement. Its reactivation during Early to Middle Pleistocene was responsible for the emplacement of andesitic to dacitic lava flows and domes of La Cieneguilla Supersynthem. The NE–SW San Antonio fault system was active during Late Pliocene, before the reactivation of the Taxco–Querétaro fault system, and is characterized by extensional left-lateral oblique-slip kinematics. The youngest is the E–W Tenango fault system that has been active since Late Pleistocene. This fault system is characterized by transtensive left-lateral strike-slip movement, and partly coeval with the youngest eruptive phase, the Nevado Supersynthem, which formed the present summit cone of the Nevado de Toluca volcano. The stress re-orientation from the Taxco–Querétaro to the Tenango fault system during Late Pleistocene is responsible for the ∼ 1 Ma hiatus in the magmatic activity between 1.15 Ma and 42 ka. After this period of repose, the eruptive style drastically changed from effusive to explosive with the emission of dacitic products. The methodology presented here furnish new data that can be used to better assess the complex structural evolution of this sector of the Trans Mexican Volcanic Belt and to understand the influence of changes in the tectonic setting on the growth of volcanic edifices.

Subpixel analysis of Landsat ETM/sup +/ using self-organizing map (SOM) neural networks for urban land cover characterization

This paper examines the subpixel analysis of Landsat ETM/sup +/ data to estimate the percent cover of impervious surface, lawn, and woody tree cover in typical urban/suburban landscapes. By combining Self-Organizing Map (SOM), Learning Vector Quantization (LVQ), and Gaussian Mixture Model (GMM) methods, the posterior probability of the various land cover components were estimated for each pixel as a means of subpixel analysis. The estimation of impervious surface and the differentiation of urban vegetation-grass versus woody tree cover-are the main objectives of this paper. Overall, the output estimates compared favorably with those obtained using higher spatial resolution aerial photograph and IKONOS satellite image and traditional hard classification techniques as independent reference. The SOM-LVQ-GMM model showed a moderate degree of similarity in the estimates of impervious surface [root mean-square errors (RMSEs) of </spl plusmn/12% for the aerial photo reference plots and </spl plusmn/18% for the IKONOS classified results at a 3/spl times/3 pixel scale]. The vegetation components of woody tree and grass cover had an RMSE of </spl plusmn/10% and 11% for the aerial photo reference plots and </spl plusmn/15% and 22% for the IKONOS classified results at a 3/spl times/3 pixel scale, respectively. While further work is needed to improve the partition of grass versus woody tree cover estimation, the SOM-LVQ-GMM approach was sufficient to effectively discriminate between those areas dominated by grass cover versus those with significant woody tree cover. The ability to separate the grass versus woody tree components in urban vegetation analysis provides a more nuanced view of urban ecosystems.

The Earth on the Web

ALTHOUGH I have always been fascinated with geography, I do not have fond memories of geography class. Most of my days in geography were spent labeling all kinds of black-andwhite outline maps of portions of the Earth. I even vaguely remember taking a test where I had to memorize and label 20 or so of the major rivers of Africa. Of all the curriculum areas that technology gives us the power to transform, geography may top the list. If I were building a high-tech middle school or high school, I would make a special computer lab for geography a high priority. I would also build a computer lab dedicated to the Earth sciences. Within the last five years or so, major websites such as Google, Microsoft, Yahoo, and various U.S. government sites have made it possible to conveniently view all kinds of high-resolution images and maps of the Earth's surface. Today, there is no longer a need for outline maps in geography classes. Students can simply fire up a browser and study an aerial photograph of the features of interest. Google Earth, released last June, has garnered a lot of attention, but Google is just one site offering Earth imaging. In this column I present an overview of several major Earth-imaging sites. Of course, to incorporate Web-based imaging productively into the classroom requires some planning, but it's fun planning. Microsoft's TerraServer website at http:// terraserver-usa.com was one of the first sites to offer high-resolution aerial photographic images of the U.S., mostly obtained from the U.S. Geological Survey (USGS). The TerraServer images are in black and white, but the resolution is incredible. You can zoom in close enough to pick out individual houses in towns across the country. The images on the TerraServer seem to be particularly detailed when they feature navigable rivers and waterways. I suppose the USGS likes to keep the Navy and the merchant marine industry well informed. Just last weekend I used TerraServer to study the Atlantic Intracoastal Waterway near my house to help find potentially good fishing sites. Waterway features such as sandbars and deep holes are relatively easy to pick out on TerraServer images. (Incidentally, did you know that Microsoft CEO Bill Gates owns the rights to more pictures and images than anyone else in the world?) Aside from NASA, the USGS probably has more maps and images than anyone else in the world. There is an excellent listing of Earth-imaging sites at http://education.usgs. gov/common/map_databases.htm. The USGS also has a site that graphically displays image databases by category at http://rockyweb. cr.usgs.gov/outreach/mapcatalog. Categories on this site include topography, geology, image, culture and history, international and world, and environmental. I visited the culture and history site and found an interesting historical map of the Lewis and Clark expedition. My Mac's Web browser, Safari, crashed while trying to download the map, which was a 16.8-MB file, so I switched to Internet Explorer, which successfully downloaded the map. While at the USGS site, I also downloaded a high-resolution orthographic image of my home state of Nebraska. This was a 98-MB image file that took about 12 minutes to download using Internet Explorer. Once downloaded, the only software I could get to open an image file this size--19,593 x 11,922 pixels--was PhotoShop 7. I mention these details to point out why schools will need a specialized geography lab with fast computers, a high-speed Internet connection, and network storage. To further illustrate the need for a specialized lab, consider the recommended requirements for Google Earth. Google recommends the following computer configuration: Windows XP; 2.4-GHz processor; 512-MB memory (I would insist on 1 GB); a 3-D graphics card, with 32-MB video memory; and a 1280 x 1024, 32-bit true color screen. That is not to say that you can't enjoy Earth-imaging sites without such a computer. …

Detecting Roman land boundaries in aerial photographs using Radon transforms

Remotely sensed images are a valuable resource for archaeological landscape studies. Historical aerial photographs, in particular, often contain important data, especially where recent landscape change has drastically altered topography. Within the current study area, focussed upon the alluvial landscape surrounding the ancient city of Butrint in southern Albania, late 20th century agricultural intensification has obliterated topographical features relating to earlier land-use within the valley. However, through recourse to earlier aerial photographic images and the development of an image analysis procedure utilizing Radon transforms, a study of relic landscape divisions relating to the Roman settlement and land-use at Butrint has been possible. The analytical procedure described allows the rapid, automated detection of linear alignments relating to the orientation of the settlement over large spatial areas. The resulting data were imported into a GIS, allowing measurements between surviving linear elements to be made and regular patterns of land division or centuriation deduced. The study revealed the surviving remnants of a centuriation pattern composed primarily of 20 actus divisions, while a further possibly earlier pattern was also detected, based upon 16 by 24 actus divisions.

Structural analysis of the collar of the Vredefort Dome, South Africa—Significance for impact‐related deformation and central uplift formation

Abstract— Landsat TM, aerial photograph image analysis, and field mapping of Witwatersrand supergroup meta‐sedimentary strata in the collar of the Vredefort Dome reveals a highly heterogeneous internal structure involving folds, faults, fractures, and melt breccias that are interpreted as the product of shock deformation and central uplift formation during the 2.02 Ga Vredefort impact event. Broadly radially oriented symmetric and asymmetric folds with wavelengths ranging from tens of meters to kilometers and conjugate radial to oblique faults with strike‐slip displacements of, typically, tens to hundreds of meters accommodated tangential shortening of the collar of the dome that decreased from ˜17% at a radius from the dome center of 21 km to &lt;5% at a radius of 29 km. Ubiquitous shear fractures containing pseudotachylitic breccia, particularly in the metapelitic units, display local slip senses consistent with either tangential shortening or tangential extension; however, it is uncertain whether they formed at the same time as the larger faults or earlier, during the shock pulse. In addition to shatter cones, quartzite units show two fracture types—a cmspaced rhomboidal to orthogonal type that may be the product of shock‐induced deformation and later joints accomplishing tangential and radial extension. The occurrence of pseudotachylitic breccia within some of these later joints, and the presence of radial and tangential dikes of impact melt rock, confirm the impact timing of these features and are suggestive of late‐stage collapse of the central uplift.

Morphological analysis of Nevado de Toluca volcano (Mexico): new insights into the structure and evolution of an andesitic to dacitic stratovolcano

We present a morphological analysis of Nevado de Toluca volcano located 80 km WSW of Mexico City based on digital elevation model study, where slope and aspect maps have been generated and analysed. Aerial photograph and satellite image observations improve the morphological analysis. The synoptic view which is offered by this analysis allowed for recognition and localization of the main volcanic and tectonic features of the area. On the basis of digital elevation model value distribution and surface textures, five morphological domains were defined. The most interesting domain, south of the crater, reflects the occurrence of an ancient complex volcano distinct from the adjacent areas. Interaction between the volcanic and volcano–tectonic evolution and the basement produced the other domains. Single volcanic edifices, like lava domes and scoria cones, and eruptive fractures were recognized. Finally, flank collapse scarps opened to the east and to the north were identified and four relevant morphostructural lineaments and their possible role in the Nevado de Toluca geological and structural evolution are discussed.

Field Scale Mapping of Surface Soil Clay Concentration

The surface soil clay concentration is a useful soil property to map soils, interpret soil properties, and guide irrigation, fertilizer, and agricultural chemical applications. The objective of this study was to determine whether surface soil clay concentrations could be predicted from remotely sensed imagery of bare surface soil or from soil electrical conductivity for a 115 ha field located in Crisp County, Georgia. The soil clay concentrations were determined for soil samples taken at 28 field locations. Three different data sources–an aerial color photograph image, two infrared bands from an ATLAS data set, and the electrical conductivity of the surface soil layer were used in the research. Principal components analysis was applied to the color photograph image, whereas the ratio of two infrared bands was applied to the ATLAS data set. Filtering was applied to both resulting images. The distribution of soil electrical conductivity was derived from the measured soil electrical conductivity data by spatial analysis. Statistical relationships between soil clay concentrations and the principal component 3, the ratio of two ATLAS infrared bands, and the soil electrical conductivity were analyzed, and three linear equations were derived with r 2 values 0.83, 0.52, and 0.78, respectively. The distribution of the soil clay concentrations was derived based on these three equations. Six levels of soil clay concentrations were classified in these three methods, and the advantages and disadvantages were discussed. The predicted and measured soil clay concentrations, based on additional soil samples from 30 field locations, were compared using linear regression (r 2=0.76, 0.45, and 0.77 for the three methods). The overall accuracy for these methods were 84%, 66%, and 76%, respectively. The principal components method had the highest accuracy in our research, while the result for the depressional areas is the best from the ratio method.

A surge of Perseibreen, Svalbard, examined using aerial photography and ASTER high resolution satellite imagery

The identification of surge activity is important in assessing the duration of the active and quiescent phases of the surge cycle of Svalbard glaciers. Satellite and aerial photographic images are used to identify and describe the form and flow of Perseibreen, a valley glacier of 59 km2 on the east coast of Spitsbergen. Heavy surface crevassing and a steep ice front, indicative of surge activity, were first observed on Perseibreen in April 2002. Examination of high resolution (15 m) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery confirmed this surge activity. Perseibreen retreated by almost 750 m between 1961 and 1990. Between 1990 and the summer of 2000, Perseibreen switched from retreat and its front began to advance. Rapid advance was underway during the period June 2000 to May 2001, with terminus advance at over 400 m yr?1. Between May and August 2001 the rate increased to over 750 m yr?1. The observed crevasse orientation indicates that ice was in longitudinal tension, suggesting the down-glacier transfer of mass. Ice surface velocities, derived from image correlation between ASTER images, were 2-2.5 m d?1 between May and August 2001. The glacier was flowing at a relatively uniform speed with sharp velocity gradients located close to its lateral margins, a velocity structure typical of ice masses in the active phase of the surge cycle. The stress regime is extensional throughout and the surge appears to be initiated low on the glacier. This is similar to the active-phase dynamics of other Svalbard tidewater glaciers. Perseibreen has probably been inactive since at least 1870, a period of about 130 years to the present surge which defines a minimum length for the quiescent phase.

Configuration and timing of Ungava Bay ice streams, Labrador–Ungava, Canada

The prominent Ungava Bay landform swarm (UBLS), covering an area of ˜260000 km2 south of Ungava Bay, Canada, is defined by drumlins, crag‐and‐tails, horned crag‐and‐tails and flutes indicating convergent ice flow towards Ungava Bay. The UBLS has been difficult to interpret in terms of ice‐sheet configuration, dynamics and age. Aerial photograph and satellite image interpretations of the Labrador‐Ungava region reveal a previously unrecognized level of complexity within the UBLS consisting of several well‐defined segments, most interpreted as representing discrete stream‐flow events. Each of the segments is characterized by one or more of the criteria (convergent flow patterns at their heads, attenuated till lineations and abrupt lateral margins) previously suggested as diagnostic for formation by fast‐flowing ice (ice streams). The UBLS reflects the most direct and probably fastest contact (in terms of sediment transport) between the Laurentide Ice Sheet interior and the ocean. It is therefore a prime candidate for abrupt changes in glacial‐age northwest Atlantic seafloor sedimentation.

A surge of Perseibreen, Svalbard, examined using aerial photography and ASTER high resolution satellite imagery

The identification of surge activity is important in assessing the duration of the active and quiescent phases of the surge cycle of Svalbard glaciers. Satellite and aerial photographic images are used to identify and describe the form and flow of Perseibreen, a valley glacier of 59 km2 on the east coast of Spitsbergen. Heavy surface crevassing and a steep ice front, indicative of surge activity, were first observed on Perseibreen in April 2002. Examination of high resolution (15 m) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery confirmed this surge activity. Perseibreen retreated by almost 750 m between 1961 and 1990. Between 1990 and the summer of 2000, Perseibreen switched from retreat and its front began to advance. Rapid advance was underway during the period June 2000 to May 2001, with terminus advance at over 400 m yr?1. Between May and August 2001 the rate increased to over 750 m yr?1. The observed crevasse orientation indicates that ice was in longitudinal tension, suggesting the down-glacier transfer of mass. Ice surface velocities, derived from image correlation between ASTER images, were 2-2.5 m d?1 between May and August 2001. The glacier was flowing at a relatively uniform speed with sharp velocity gradients located close to its lateral margins, a velocity structure typical of ice masses in the active phase of the surge cycle. The stress regime is extensional throughout and the surge appears to be initiated low on the glacier. This is similar to the active-phase dynamics of other Svalbard tidewater glaciers. Perseibreen has probably been inactive since at least 1870, a period of about 130 years to the present surge which defines a minimum length for the quiescent phase.

Configuration and timing of Ungava Bay ice streams, Labrador-Ungava, Canada

The prominent Ungava Bay landform swarm (UBLS), covering an area of ˜260000 km2 south of Ungava Bay, Canada, is defined by drumlins, crag-and-tails, horned crag-and-tails and flutes indicating convergent ice flow towards Ungava Bay. The UBLS has been difficult to interpret in terms of ice-sheet configuration, dynamics and age. Aerial photograph and satellite image interpretations of the Labrador-Ungava region reveal a previously unrecognized level of complexity within the UBLS consisting of several well-defined segments, most interpreted as representing discrete stream-flow events. Each of the segments is characterized by one or more of the criteria (convergent flow patterns at their heads, attenuated till lineations and abrupt lateral margins) previously suggested as diagnostic for formation by fast-flowing ice (ice streams). The UBLS reflects the most direct and probably fastest contact (in terms of sediment transport) between the Laurentide Ice Sheet interior and the ocean. It is therefore a prime candidate for abrupt changes in glacial-age northwest Atlantic seafloor sedimentation.

空撮画像の同質領域判定による九州北部里山林の樹冠抽出に関する研究

This paper attempts to extract data for forest crowns analysis by the determining same color regions method of image processing. For the analysis of crown size aerial photographic RGB images of broad leaved forest, also of Cryptomeria japonica and Chamaecyparis obtuse forest, of a Northern Kyushu Satoyama Rural Forest were utilized. The Image color distribution was used as an image feature. At first, the circle was calculating at every pixel less than the range of the determined standard value (h) of the color. Next, diffuseness information such as shadow areas and overlapping circles were eliminated from images. Remaining dot images were the processing data for the crown. In each of the research plot, verification data of crown width and number was ascertained by observations, and then compared with processed data. As a result, broad leave forest was determined have the best accuracy for extracting crown width at h: 40, and Cryptomeria japonica and Chamaecyparis obtuse forests were h: 15 to 20. However crown numbers were counted at less than 50% of the original images, because of the characteristics of this image processing method.

Extent and Dispersal Rates of Chinese Privet ( Ligustrum sinense ) Invasion on the Upper Oconee River Floodplain, North Georgia

Ligustrum sinense (Chinese privet, privet) is an invasive woody shrub with an extensive naturalized distribution in the eastern and southeastern United States. Although privet is considered an invasive species in many eastern states, to date there has been no attempt to quantify the areal extent of privet invasions in vulnerable ecosystems. In the Upper Oconee River Basin, northeastern Georgia, privet thickets are abundant on the river floodplain. At the landscape scale, I used historical aerial photographic analysis to determine the extent and timing of privet invasion along a 43 km reach of the Upper Oconee River I also used magnified historical aerial photograph images to investigate whether there are particular types of land uses associated with the invasion at three one-kilometer sub-reaches Privet was well established by 1951, the first aerial photographs of the area taken during winter leaf-off period, when 51% of 1,327 ha of floodplain surface had already been invaded. By 1999 privet had spread to 59% of the floodplain Analysis of the 43-km study reach, and qualitative observations of historical privet invasion at the three representative sub-reaches, suggest that the modest increases in privet extent over the study period are primarily due to invasion of agricultural fields and pastures. While some remnant patches of noninvaded floodplain forest persist in areas that experienced less human activity, most remaining stands of noninvaded floodplain forest are confined to backswamp areas where frequent flooding appears to exclude privet establishment and growth.

MANGROVE MAPPING USING LANDSAT IMAGERY AND AERIAL PHOTOGRAPHS: KEMAMAN DISTRICT, TERENGGANU, MALAYSIA

Classification and distribution of mangrove vegetation are vital information for the proper development of a mangrove management plan. In this study, classification for the mangroves of the district of Kemaman were done using both 1 : 5000 aerial photographs and Landsat TM imageries. The coverage by aerial photographs is limited to the coastal and estuarine areas only. Thus, for areas further upstream of the aerial photo coverage, Landsat TM imageries were used. Analysis of aerial photographs and remote sensing images revealed that the mangroves of Kemaman could be classified into 14 different classes of vegetation. All the 14 classes were identified from areas covered by the aerial photographs. For areas covered by the Landsat images only 7 classes of vegetation were identified. The accuracy for aerial photograph and Landsat images are 91.2% and 87.8%, respectively. It can be concluded that although both techniques are useful in determining the mangrove vegetation classes, the large 1 : 5000 aerial photographs are more accurate and provided more detailed information comparatively.

Observation: Long-Term Increases in Mesquite Canopy Cover in a North Texas Savanna

It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to determine the economic feasibility of treatments designed to manage these plants. This study observed changes in honey mesquite (Prosopis glandulosa Torr.) canopy cover over a 20-year period (1976-1995) in 2 treatments: an untreated area that initially had a moderately dense mesquite stand (14.6% cover), and an area cleared of mesquite with root-plowing in 1974. Canopy cover of mesquite was estimated from scanned color-infrared aerial photograph images by manually delineating mesquite canopies with a computer using ArcView software. During the 20 years, mesquite cover in the untreated area increased (P less than or equal to 0.05) from 14.6 to 58.7%, averaging 2.2 percentage units per year. Cover in the root-plow treatment also significantly increased during the same period from 0 to 21.9% (1.1 percentage units per year), but the rate of increase was significantly lower than in the untreated area because mesquite growth was from new seedlings instead of established plants and/or new seedlings as occurred in the untreated area. Rate of increase was significantly lower from 1976 to 1990 (1.6 and 0.2 percentage units per year) than from 1990 to 1995 (4.1 and 3.7 percentage units per year) in the untreated and root-plow treatment, respectively. These differences were attributed to precipitation which was near normal from 1976 to 1990 but 25% above normal from 1991 to 1995. DOI:10.2458/azu_jrm_v54i2_ansley

Detecting and Enumerating New Building Structures Utilizing Very‐High Resolution Imaged Data and Image Processing

Information on the number and type of new building structures is required by urban and transportation planners and the real estate industry. The goal of this paper is to explore the potential of high resolution imagery for meeting public and private sector demands for information on new buildings. The value of 1 m, 5 m, and 10 m panchromatic and 1 m color scanned aerial photography images acquired in 1997 and 1998 for a study area within the City of San Diego, California is assessed for general change detection and building enumeration. Both semi‐automated and interactive change‐detection approaches are evaluated. We demonstrate that interactive, visual‐based approaches appear to be the most accurate (within 1% of actual count) and efficient approach for generating information on the number of new buildings associated with single family residential land use. More automated approaches to detecting and enumerating image microfeatures may be useful as enhancements for visual‐based assessments and may be practical in areas composed mostly of large buildings associated with commercial and industrial land use. The highest accuracy for automated approaches was an undercounting of 11% for residential buildings and overcounting of 20% for those associated with commercial and industrial land use.

Climbing Scale and Place: Geological Musings and Social Geographical Method

********** This paper retrospectively examines my two years of doctoral fieldwork in the palace of Kano, Nigeria, where I integrated my former training as a geologist into social geographical field research. At the time, I used this geological training to intuit what was methodologically required in a social context, never having had formal fieldwork training in geography. I have recently come to see that much of my methodological matter-of-factness derived from the fact that I had had years of undergraduate and graduate geological field training and that I had worked as a practicing geologist for several years (Figure 1). (1) The naturalness with which I approached the field was, in retrospect, surprisingly tempered by previous geological practice: collecting and analyzing aerial photographic images and settlement pattern maps, mapping in detail palace arrangements and material contents, picking out structural relationships in the landscapes, and so on. I now realize that my geological training taught me significant skills that translated into the worlds of the social--especially with respect to the many geological means for mapping out larger territorial histories of structural transformation by cataloguing the microhistories of rock fabrics. My senior thesis on an area in Rhode Island and, later, my master's thesis on an area in New Brunswick (Canada), for example, required that I make microscopic slides or thin sections of various rock fabrics from the Appalachian Mountains. These were analyzed for microspatial textures indicative of large-scale regional deformation over time. By charting the micropatterns of hundreds of thin sections on a circular map that translated microscopic measurements into a three-dimensional context, I could literally project, and hence identify, certain patterns of historical regional deformation. Such transform mapping revealed four phases of deformation and pointed to differential and historically staggered axes of geological compression. Later investigative work involving thick (fluid-inclusion) sections enabled me to determine overall formational pressures and temperatures of different rock fabrics. In some ways, the variously sectioned rock tissues spoke in metaphorically holographic and fractal detail: Certain regional pressures registered readably in the microfabrics of rock samples chipped away strategically from sites in the area of interest; the microscopy of the rock fabrics, in turn, hinted that certain details of the events registered at still smaller scales of analysis. Indeed, using an electron microprobe on yet another type of rock section, chemical variations across discrete minerals could be discerned. This chemical information, along with other data, would eventually be combined to relay evolutionary changes in fluid chemistries, pressures, and temperatures that had formed, deformed, metamorphosed, and/or shattered the geological formations I was studying (Nast and Williams-Jones 1991). Of equal importance, these findings were supposed to be of some practical use. The New Brunswick research was funded by corporate interests that expected me to develop exploration guidelines based on my knowledge of how surface expressions relayed information about deeper ore-depositing conditions. Providing my financiers with surface-based clues for locating similar ore deposits at depth--say, a list of visible minerals or mineral combinations on the earth's surface and/or certain sets of fracture patterns--presumed that similar heat-pressure-chemistry conditions produced similar sorts of ores, not only in New Brunswick but elsewhere in the world. What is important here is that my geological training presumed that micro- and macroanalyses were translatable across scales and across place. In fact, the discipline of geology is rife with methodological means for analytically climbing across contexts and scales, allowing for the creation of stories about large-scale deformational events within region, locale, rock, and discrete minerals--and vice versa. …

Observation: Long-term increases in mesquite canopy cover in a north Texas savanna

It is necessary to quantify rates of woody plant encroachment on southwestern USA rangelands to determine the economic feasibility of treatments designed to manage these plants. This study observed changes in honey mesquite (Prosopis glandulosa Torr.) canopy cover over a 20-year period (1976-1995) in 2 treatments: an untreated area that initially had a moderately dense mesquite stand (14.6% cover), and an area cleared of mesquite with root-plowing in 1974. Canopy cover of mesquite was estimated from scanned color-infrared aerial photograph images by manually delineating mesquite canopies with a computer using ArcView software. During the 20 years, mesquite cover in the untreated area increased (P less than or equal to 0.05) from 14.6 to 58.7%, averaging 2.2 percentage units per year. Cover in the root-plow treatment also significantly increased during the same period from 0 to 21.9% (1.1 percentage units per year), but the rate of increase was significantly lower than in the untreated area because mesquite growth was from new seedlings instead of established plants and/or new seedlings as occurred in the untreated area. Rate of increase was significantly lower from 1976 to 1990 (1.6 and 0.2 percentage units per year) than from 1990 to 1995 (4.1 and 3.7 percentage units per year) in the untreated and root-plow treatment, respectively. These differences were attributed to precipitation which was near normal from 1976 to 1990 but 25% above normal from 1991 to 1995.