Color Infrared Research Articles

Aerial Color Infrared Photography for Determining Early In‐Season Nitrogen Requirements in Corn

In‐season determination of corn (Zea mays L.) N requirements via remote sensing may help optimize N application decisions and improve profit, fertilizer use efficiency, and environmental quality. The objective of this study was to use aerial color‐infrared (CIR) photography as a remote‐sensing technique for predicting in‐season N requirements for corn at the V7 growth stage. Field studies were conducted for 2 yr at three locations, each with and without irrigation, in the North Carolina Coastal Plain. Experimental treatments were a complete factorial of four N rates at planting (NPL) and five N rates at V7 (NV7). Aerial CIR photographs were taken at each of the locations at V7 before N application. Optimum NV7 ranged from 0 to 207 kg N ha−1 with a mean of 67 kg N ha−1. Significant but weak correlations were observed between optimum NV7 rates and the band combinations relative green, Relative Green Difference Vegetation Index, and Relative Difference Vegetation Index as measured in CIR photos. High proportions of soil reflectance in the images early in the corn growing season (V7) likely confounded our attempts to relate spectral information to optimum NV7 rates. The primary obstacles to applying this technique early in the season are the use of relative digital counts or indices that require high‐N reference strips in the field and strong background reflectance from the soil. When the NPL treatments that were nonresponsive to NV7 (i.e., optimum NV7 = 0) were removed from the analysis, the normalized near infrared, the Green Difference Vegetation Index, the Green Ratio Vegetation Index, and the Green Normalized Difference Vegetation Index were the best predictors of optimum NV7 rate (r2 = 0.33).

Quantitative imaging to measure photosynthetic biomass on an intertidal rock-platform

Conventional methods for measuring amounts of epilithic photosynthetic biomass in intertidal habitats by estimating amounts of chlorophyll in rock samples are imprecise, laborious and destructive. An alternative remote sensing method for quantifying chlorophyll amounts at small spa- tial scales using field-based digital colour-infrared (CIR) imagery is presented. CIR images were obtained from 4 areas of the emersed rock-platform. Experimental plots were initially scraped to remove any macro- or micro-algae. After different periods of recolonization of micro-algae, images of the plots were acquired under full sunlight or under artificial shade, before and after the rocks were uniformly wetted. Samples of rock were taken for laboratory determination of amount of chlorophyll. Relative absorption by chlorophyll was estimated from CIR data using a ratio of near-infrared (NIR) and red bands. The image ratios were validated by comparing them to data from a field spectrome- ter. Measurements of the amount of chlorophyll extracted from rock samples were linearly related to estimates from the NIR:red ratio. Ratios derived from images acquired under full sunlight, before and after wetting the surface, had the strongest relationship with chlorophyll (r 2 = 0.84 and 0.83, respec- tively). Artificial shading of the rock reduced the strength of the relationship between chlorophyll and the NIR:red ratio before and after wetting (r 2 = 0.79 and 0.63, respectively). Micro-algae in scraped areas and micro- and macro-algal mixtures could be estimated using the same equation. The technique enables rapid contiguous in situ measurements of chlorophyll to be made without the microflora being destroyed and will facilitate more comprehensive studies of competitive interactions among intertidal grazing animals.

Attempt to Validate a Remote Sensing‐Based Late‐Season Corn Nitrogen Requirement Prediction System

Recent research showed that corn (Zea mays L.) may respond profitably to N applied at tasseling (VT), and that aerial color-infrared (CIR) photography could be used to predict economic optimum N rates at VT using the green difference vegetation index (GDVI, near-infrared brightness minus green brightness) calculated relative to a high N reference strip (relative GDVI, RGDVI). This technique could be used by farmers to identify N stress and quantify N requirements. To validate this technique for practical application, experiments were conducted with different rates of N applied at planting and at VT on irrigated and non-irrigated sites in North Carolina during 2003. In both irrigated and non-irrigated systems, maximum yield potential was achieved with 200 lb of N per acre at planting. The difference between predicted and observed optimum N rate at VT ranged from -27 to 80 lb/acre. Greater differences between predicted and observed optimum N rate at VT occurred when N requirement was high, which was attributed to lower yield potential in 2003 compared to the years when the model was developed. Although the model tended to over-predict N rates, it did capture differences in N requirements across the range of conditions tested, indicating that this technique can be an effective tool to determine late-season corn N need. Differences between the estimated and actual N rates might be reduced by incorporating a method for determining yield potential.

Novel use of digital colour-infrared imagery to test hypotheses about grazing by intertidal herbivorous gastropods

Colour-infrared (CIR) imagery was evaluated for its usefulness to test hypotheses about grazing in the intertidal gastropods Nerita atramentosa (Reeve) and Bembicium nanum (Lamarck). Tiles of natural sandstone were placed onto the shore to accumulate micro-algae for a period of 6 weeks. Then, in the laboratory, three replicate tiles were assigned into each of 6 treatments ( Nerita and Bembicum at densities of 3 or 6 animals, plus a control and a control for artifacts due to cages). CIR images were acquired before and three times after the animals were placed on the tiles. NIR / red ratio images, which are used to estimate micro-algal biomass, were generated from calibrated CIR data. Nerita at the greater density were more effective at removing micro-algae than at the smaller density. The latter were more effective than Bembicium at either density, which did not significantly decrease algal biomass from that in controls. These data are consistent with previous field observations and indicate that CIR imagery is an effective method for testing hypotheses about grazing by intertidal gastropods.

Grayscale aerial and space image colorization using texture classification

This paper introduces a new approach to colorization of grayscale aerial or space imagery. Proposed method is based on a simple premise: similar textures should have similar color distributions. This premise is formalized by using Bayesian texture classification of grayscale destination imagery with a set of textural prototypes or swatches from source color imagery. Only 2D distributions of chrominance channels are transferred and original luminance value is retained. A special segmentation technique is proposed in order to increase the performance of the algorithm. Examples on real images show high quality of colorization neither without using low-resolution color imagery nor without any user intervention. Appropriate prototype selection enables modeling of season changes of vegetation. It is shown that the proposed approach can be successfully applied to color infrared (CIR) imagery transform into visible RGB colors and for color image remapping.

Aerial Color Infrared Photography for Determining Late‐Season Nitrogen Requirements in Corn

Fast and accurate methods of determining in‐season corn (Zea mays L.) N requirements are needed to provide more precise and economical management and potentially decrease groundwater N contamination. The objectives of this study were (i) to determine if there is a response to late‐season N applied to corn at pretassel (VT) under irrigated and nonirrigated conditions, and (ii) to develop a methodology for predicting in‐season N requirement for corn at the VT stage using aerial color infrared (CIR) photography. Field studies were conducted for 3 yr over a wide range of soil conditions and water regimes in the North Carolina Coastal Plain. Different fertilizer N rates were applied (i) at planting (NPL) to create a range of N supply, corn color, and near‐infrared (NIR) radiance; and (ii) at VT (NVT) to measure yield response to NVT. Aerial CIR photographs were obtained for each site at VT before N application. Significant grain yield responses to NPL and NVT were observed. Economic optimum NVT rates ranged from 0 to 224 kg ha−1 with a mean of 104 kg ha−1. Better prediction of economic optimum NVT rates was obtained with spectral band combinations rather than individual bands, and improved when calculated relative to high‐N reference strips measured at VT. The best predictor of economic optimum NVT (R 2 = 0.67) was a linear‐plateau model based on corn color and NIR radiance expressed using the Green Difference Vegetation Index (GDVI) relative to high‐N reference strips (Relative GDVI, RGDVI).

The Effect of Spatial Resolution of Remotely Sensed Data in Dasymetric Mapping of Residential Areas

This study explores the effect of spatial resolution on outcomes of dasymetric mapping using remotely sensed data, particularly the 30 m multispectral (MS) and 15 m panchromatic (PAN) spatial resolutions of Landsat Enhanced Thematic Mapper (ETM), 15 m of ASTER, and 1 m of airborne color infrared (CIR) imagery for Black Hawk County, Iowa. These images were classified to produce urban land cover maps. Then, dasymetric maps for population density were developed using residential areas derived from remotely sensed data and various GIS layers. The effect of spatial resolution on dasymetric maps was evaluated using traditional choropleth maps and a differentiation matrix. The accuracy of dasymetric maps with different spatial resolutions was assessed using highly detailed population density maps generated from the residential building footprints. The analysis demonstrates that dasymetric maps with higher spatial resolution tend to exhibit higher levels of accuracy. However, with higher spatial resolution data, factors such as spectral resolution and shadow effects should be considered for dasymetric mapping.

Detecting vegetation changes in a wetland area in Northern Germany using earth observation and geodata

Monitoring land use and landscape dynamics in conservation areas is important to understand and influence nature and restoration processes. Earth observation data can help to detect changes automatically in extensive areas. In a wetland area in Northern Germany different change detection methods have been tested to detect wetland restoration processes, especially succession of wetland and moorland vegetation over 11 years. Therefore a change detection method based on a selective principal component analysis followed by a fuzzy membership function introduced by Weiers et al. (2001). was tested with dual date Landsat TM/ETM+ images. As comparison vegetation maps and Colour-infrared (CIR)-aerial photographs were analysed. The main objectives were to find out (1) if changes, especially vegetation changes, can be detected on the study area by the method as described by Weiers et al. (2001), (2) which changes can be detected and (3) which is the best method on the study area, respectively: the Landsat change detection method, the analysis of vegetation maps or the interpretation of CIR-aerial photographs. For detecting vegetation changes the most detailed information were achieved by interpreting CIR-aerial photographs, while the Landsat change detection method turned out to be more suitable for detecting changes of wetness.

A thermoregulatory center in hornets: IR photography

In the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae), there is on the dorsal side of the thorax, beneath the mesoscutum plate of the prothorax and around the median notal suture, a lump that, in the course of hornet activity, is warmer by 9 degrees C from the surrounding milieu and by up to 6 degrees C from other body parts of the hornet. This lump is about 1 mm in diameter, butterfly-shaped, and its upper, posterior border abuts the base of the forewings. During hornet activity and via Infra Red photography one can observe heat extensions stemming from the center of the lump and proceeding forward in the direction of the head, downward toward the legs and backwards toward the bases of the wings. The warmest region is the center of the lump, with its margins showing a lower temperature. As for the legs of the hornet, their upper part is warmer than the other parts. The temperature gradients along the hornet's body are dependent on the extent and nature of hornet activity. Thus, during flight or ventilation activity, the thorax is the warmest part of the body, while the wings, legs, and antennae, as well as the posterior part of the gaster are colder, yet all these body parts are still warmer to varying degrees than the surrounding milieu. Thus, at night, when sentry worker hornets stand guard around the nest entrance and remain practically motionless, the temperature differences between the various body parts are retained unchanged. We conjecture that the described butterfly-shaped lump is a thermoregulatory center (TC), which is neurogenically activated, since the changes occurring in it are rapid, a matter of one to several seconds and do not appear to be directly dependent on the hemolymph supply. The thermoregulatory center keeps a high constant temperature apparently related to hornet activity and the environmental conditions. The temperature cascade is most probably regulated via the tracheal system. Apparently another system activated by a heat pump mechanism keeps the gaster at a lower temperature than the environment.

The Assessment of Cutting Temperature Measurements in High-Speed Machining

High-speed machining has received important interest because it leads to an increase of productivity and a better workpiece surface quality. However, the tool wear increases dramatically in high-speed machining (HSM) operations due to the high cutting temperature at the tool-workpiece interface and chip-tool interface. Cutting temperature and its gradient play an important role in tool life and machined part accuracy. This paper reviews different methods of the measurements of cutting temperature, which include: (1) thermocouples---tool-work thermocouple, embedded thermocouple, combination thermocouple and compensation thermocouple (2) optical infrared pyrometer, (3) infra-red photography, (4) thermal paints, (5) microstructure or microhardness observation. Each method has its advantages and limitations. The fundamental principles and application fields of each measurement method are presented, which is useful for the selection of the measurement methods for high-speed cutting temperature.

Using Aerial Color‐infrared Photography and QuickBird Satellite Imagery for Mapping Wetland Vegetation

Aerial color‐infrared (CIR) photography and QuickBird high resolution (2.8 m) false color satellite imagery were evaluated for differentiating among wetland vegetation in two freshwater lakes on the Welder Wildlife Refuge in south Texas. Field spectral measurements made on dominant vegetation types (plant species and vegetation mixtures) showed significant differences in visible and near‐infrared reflectance. Several plant species and mixtures of species could be distinguished in the aerial photos and satellite imagery. Accuracy assessments performed on computer classifications of the photos of the two lakes had overall accuracies of 84% and 87%; whereas, accuracy assessments performed on classifications of the satellite imagery of the lakes had overall accuracies of 69% and 76%. The lower accuracies of the satellite image classifications were attributed to their coarser spatial resolution.

Comparison of Near Infrared Light Photography and Middle Infrared Light Photography for Deciphering Obliterated Writings

There are obliterated writings that are undecipherable by conventional visible and near infrared monochromatic light photography. Some of them could be deciphered undestructively by middle infrared light photography. Characters were written on paper with 101 kinds of pens. Middle infrared light photographs and near infrared light photographs of them were taken and compared to recognize what kinds of inks is transparent at examined wavelength regions. Based on the results obtained, the combination of ink for drawing and obliterating (which is not deciphered by visible and near infrared light photography, but expected to be deciphered with middle infrared light photography) is selected. From the examined photographs, it is demonstrated that there exist obliterated writings which are undecipherable by conventional near infrared light photography, but decipherable by middle infrared light photography.

Changes in the distribution of the grey mangrove Avicennia marina (Forsk.) using large scale aerial color infrared photographs: are the changes related to habitat modification for mosquito control?

Runnelling, a method of habitat modification used for mosquito management in intertidal saltmarshes in Australia, alters marsh hydrology. The objective of this research was to assess if runnelling had affected the distribution of the grey mangrove ( Avicennia marina (Forsk.)) at a study site in southeast Queensland. Since runnelling is carried out in diverse marshes a second aim was to assess differences in mangrove colonisation in the two main saltmarsh species in the area. These are marine couch [ Sporobolus virginicus (L.) Kunth.] and samphire [ Sarcocornia quinqueflora (Bunge ex Ung.-Stern.)]. Runnels at the study site were in an area dominated by Sporobolus. The mangrove area was measured by classifying digital color infrared (CIR) data obtained from aerial photographs acquired in 1982, which was 3 years before runnelling, and in 1987, 1991 and 1999, 2–14 years after. Changes in the spatial extent of A. marina were identified using difference images produced from post-classification change detection. The results showed that runnels did not significantly influence the distribution of A. marina at the study site. At a more detailed level differences in A. marina establishment in the Sporobolus and Sarcocornia areas were determined from counts of trees on the aerial photographs. There was a greater proportion of mangroves in Sarcocornia than Sporobolus and this increased over time. This may be related to differences in density between the plant species, to grapsid crab activity or to other edaphic conditions. There may be implications for runnelling in Sarcocornia marshes. The large increase observed in A. marina in the area generally is likely to be related to factors such as catchment modification or tidal/sea-level changes. It is concluded that runnelling has not led to mangrove establishment in the Sporobolus dominated saltmarsh.

Stand characteristics in colour-infrared aerial photographs as indicators of epiphytic lichens

Information about forest biodiversity has so far been collected mostly by using field inventories, but it is desirable to find other methods that can cover large areas at a lower cost. In a forest landscape covering 2000 ha in southern Sweden we tested if colour-infrared (CIR) aerial photographs on the scale of 1:30000 can be used to interpret forest stand characteristics correlated to the occurrence of epiphytic lichens that are Red-listed or otherwise indicate high nature conservation value ('signal species'). Using logistic regression we found that the interpreted stand variables tree height and crown structure class were significantly correlated to the occurrence of Red-listed species. For signal species, the variables tree height, percentage of southern deciduous trees and crown structure class were significantly correlated to the occurrence. The logistic regression models successfully predicted a significantly higher probability to find Red-listed species in the stands that actually contained such species compared to stands without Red-listed species. The same was true for stands with signal species. We conclude that interpretation of CIR aerial photographs could be a useful method to find certain groups of epiphytic lichens in surveys covering large areas. (Less)

Estimation of surface chlorophyll on an exposed mudflat using digital colour-infrared (CIR) photography

The usefulness of field-based digital Colour-InfraRed (CIR) photography to quantify concentrations of chlorophyll on the surface of exposed mudflats is investigated. Multiple images, each 626 mm by 467 mm, were acquired during Austral summertime using a Duncantech three-band CIR camera from two areas of mudflat in the upper reaches of Sydney Harbour. Sediment samples were obtained from within the field of view of the camera and their chlorophyll concentration was estimated spectrophotometrically. After the camera images were normalised to compensate for the effects of variations in the intensity of downwelling solar radiation, chlorophyll was estimated for each 0.9 mm square pixel using a suite of five different vegetation indices. Regression analysis was used to determine the strength of the relationship between the index values and the estimates of chlorophyll from the in situ samples. Indices constructed from near-infrared and red bands were found to have the strongest relationships with in situ chlorophyll estimates ( R 2 ranging from 0.28 to 0.79) and indices derived from near-infrared and green bands the weakest ( R 2 ranging from 0.16 to 0.22). The vegetation indices highlighted complex small-scale variability in chlorophyll distribution that was not evident in the original camera images. These findings indicate that field-based CIR photography will provide a useful tool for the non-destructive determination of benthic chlorophyll.

Comparison of methods for estimation of needle losses in Scots pine following defoliation by Bupalus piniaria

In 1996, ca. 7000 hectares of pine forests at Hökensås in SW Sweden were defoliated by the pine looper, Bupalus piniara (L.) (Lepidoptera. Geometridae). Following an aerial damage survey using CIR (colour infra red) photography, and estimation of pupal densities in the soil, ca 4000 ha of the most defoliated pine stands were sprayed in early August 1997 with Bacillus thuringiensis var. kurstaki. The control operation was succeessful but probably redundant, as no further defoliation occurred in unsprayed reference areas. In order to assess defoliation levels in different damage classes for later growth loss studies, 47 circular study plots were laid out in pine stands representing different damage and age classes. The remaining foliage was recorded for each tree using the following classes: 0, 10, 30, 50, 70, 90 and 100%. The defoliation levels in 1996 were estimated by disregarding the 1997 needle age class. Thirteen ca. 40-year-old sample trees representing different damage classes were felled, and the remaining foliage of all branches was estimated by needle age class using the above-mentioned scale. One branch in each of the whorls 1996, 1991, 1986 and 1981 was sampled and its needle dry weight was determined. The sample branch data confirmed the field observations that virtually no additional defoliation took place in 1997. The damage classes estimated from the CIR-pictures only agreed with the field damage estimates at the higher end of the damage scale. In contrast, the field estimate correlated well with plot means derived from tree-wise estimates (R2 = 0.93), and with with the calculated needle biomasses per tree (R2 = 0.90). Thus, the field damage classification was supported by the more detailed defoliation estimates, and hence forms a relevant basis for later growth loss studies.

Infrared imaging of subcutaneous veins

Imaging of subcutaneous veins is important in many applications, such as gaining venous access and vascular surgery. Despite a long history of medical infrared (IR) photography and imaging, this technique is not widely used for this purpose. Here we revisited and explored the capability of near-IR imaging to visualize subcutaneous structures, with a focus on diagnostics of superficial veins. An IR device comprising a head-mounted IR LED array (880 nm), a small conventional CCD camera (Toshiba Ik-mui, Tokyo, Japan), virtual-reality optics, polarizers, filters, and diffusers was used in vivo to obtain images of different subcutaneous structures. The same device was used to estimate the IR image quality as a function of wavelength produced by a tunable xenon lamp-based monochrometer in the range of 500-1,000 nm and continuous-wave Nd:YAG (1.06 microm) and diode (805 nm) lasers. The various modes of optical illumination were compared in vivo. Contrast of the IR images in the reflectance mode was measured in the near-IR spectral range of 650-1,060 nm. Using the LED array, various IR images were obtained in vivo, including images of vein structure in a pigmented, fatty forearm, varicose leg veins, and vascular lesions of the tongue. Imaging in the near-IR range (880-930 nm) provides relatively good contrast of subcutaneous veins, underscoring its value for diagnosis. This technique has the potential for the diagnosis of varicose veins with a diameter of 0.5-2 mm at a depth of 1-3 mm, guidance of venous access, podiatry, phlebotomy, injection sclerotherapy, and control of laser interstitial therapy.

Agriculture Field Characterization Using Aerial Photograph and Satellite Imagery

Successfully delineating management zones that differ in crop productivity is an important component of site-specific management. We compared the effectiveness of the digitally scanned color aerial infrared photographs and digital Landsat Thematic Mapper (TM) data for delineating within-field zones. The zones delineated using normalized difference vegetation index (NDVI) from TM data explained 34% of field yield variance compared with 9% for that from digitally scanned color aerial infrared photograph data. The zones from NDVI using Landsat TM were better able to capture spatial differences in plant growth and relatively stable soil attribute of surface soil organic carbon.

Understanding Color Infrared and Beyond

This paper presents the view that a fundamental understanding of the color infrared (CIR) format in remote sensing is the key to understanding all false color formats. Teaching approaches, demonstration equipment, sample images, and student handouts are given to show how this ‘understanding’ is accomplished in the classroom for a university introductory level principles of remote sensing course. The article is divided into three parts; part I deals with how to demonstrate additive color mixing and how to connect color theory with basic CIR signatures; part II shows how ground‐based normal color/CIR photographic pairs can strengthen student understanding of CIR signatures; and part III introduces a universal color truth table for use with CIR and any other false color satellite image composite. An example is given to show how adding spatial context (in the form of hillshading derived from a digital elevation model) into the false color composite will improve the student's signature comprehension ability. A brief discussion of lab exercises, including station‐to station image identification/interpretation problems and an aerial photography field trip conclude, the article.

Automated Change Detection for Updates of Digital Map Databases

Updating digital map databases to reflect continuous changes is a major task, which could be significantly reduced by introducing an automated change-detection process. We suggest an algorithm inspired by the specific problem of updating the Danish National Topographic Map Database (TOP10DK). The emphasis is on buildings, which are very important mapping objects. The algorithm uses vector and spectral data as input to an unsupervised spectral classification method which controls a subsequent Mahalanobis classification step. For evaluation, we present four test cases based on the TOP10DK database in combination with RGB and color-infrared (CIR) aerial photos. A main problem is roofs covered with roofing felt, which are hard to discriminate spectrally from roads. Apart from that, RGB photos are barely sufficient for change detection, while CIR data give more satisfactory results. Refinements are, however, still needed to reduce the number of false alarms.