Use Of Photogrammetric Techniques Research Articles

Teknik fotogrametri untuk mendapatkan model studi digital tiga dimensi dalam perawatan ortodonti

In the field of orthodontics, study models play an important role as diagnostic aids, photogrammetry techniques are used to obtain three-dimensional digital study models. This study model provides an accurate representation of the patient's teeth and occlusion, as well as assists in identifying dental and bone anomalies. In the creation of study models, traditional techniques using cement or gypsum are time-consuming and prone to inaccuracies. Three-dimensional scanning is the process of collecting and analyzing real-world objects or environments using digital data against their possible shapes and appearances. The collected digital data is then processed using three-dimensional scanning software so that it can be used to create three-dimensional digital models. Therefore, the use of photogrammetric techniques can improve efficiency and accuracy in orthodontic treatment. Photogrammetry requires several stages and the necessary equipment to produce good results. Photogrammetry itself has advantages and disadvantages. The three-dimensional digital study model is a better alternative to the traditional study model because it is not susceptible to physical damage, requires small digital storage space, can be transmitted instantly electronically, is a means of educating patients, and can be manipulated virtually.

The SmartLandMaps Approach for Participatory Land Rights Mapping

Millions of formal and informal land rights are still undocumented worldwide and there is a need for scalable techniques to facilitate that documentation. In this context, sketch mapping based on printed high-resolution satellite or aerial imagery is being promoted as a fit-for-purpose land administration method and can be seen as a promising way to collect cadastral and land use information with the community in a rapid and cost-effective manner. The main disadvantage of paper-based mapping is the need for digitization to facilitate the integration with existing land administration information systems and the sustainable use of the data. Currently, this digitization is mostly done manually, which is time-consuming and error-prone. This article presents the SmartLandMaps approach to land rights mapping and digitization to address this gap. The recording involves the use of sketches during participatory mapping activities to delineate parcel boundaries, and the use of mobile phones to collect attribute information about spatial units and land rights holders. The digitization involves the use of photogrammetric techniques to derive a digital representation from the annotated paper maps, and the use of computer vision techniques to automate the extraction of parcel boundaries and stickers from raster maps. The approach was deployed in four scenarios across Africa, revealing its simplicity, versatility, efficiency, and cost-effectiveness. It can be regarded as a scalable alternative to traditional paper-based participatory land rights mapping.

Automated pipeline reconstruction using deep learning & instance segmentation

BIM is a powerful tool for the construction industry as well as for various other industries, so that its use has increased massively in recent years. Laser scanners are usually used for the measurement, which, in addition to the high acquisition costs, also cause problems on reflective surfaces. The use of photogrammetric techniques for BIM in industrial plants, on the other hand, is less widespread and less automated. CAD software (for point cloud evaluation) contains at best automated reconstruction algorithms for pipes. Fittings, flanges or elbows require a manual reconstruction. We present a method for automated processing of photogrammetric images for modeling pipelines in industrial plants. For this purpose we use instance segmentation and reconstruct the components of the pipeline directly based on the edges of the segmented objects in the images. Hardware costs can be kept low by using photogrammetry instead of laser scanning. Besides the autmatic extraction and reconstruction of pipes, we have also implemented this for elbows and flanges. For object recognition, we fine-tuned different instance segmentation models using our own training data, while also testing various data augmentation techniques. The average precision varies depending on the object type. The best results were achieved with Mask R–CNN. Here, the average precision was about 40%. The results of the automated reconstruction were examined with regard to the accuracy on a test object in the laboratory. The deviations from the reference geometry were in the range of a few millimeters and were comparable to manual reconstruction. In addition, further tests were carried out with images from a plant. Provided that the objects were correctly and completely recognized, a satisfactory reconstruction is possible with the help of our method.

Documentación y análisis de un cepo de ancla romano y sus elementos iconográficos y epigráficos sellados

This paper aims to present the documentation and analysis methodology carried out on a lead trap from the ancient period, which belongs to the collection of traps in the Museum of Cádiz (Andalusia, Spain). The anchor stock had some interesting characteristics for this research. On the one hand, from the point of view of conservation and restoration, due to the alterations it presented. On the other hand, from a historical and archaeological point of view, it showed signs of reliefs on its surface hidden under the alteration products. The removal of the different layers of alteration that covered the surface during conservation and restoration treatments revealed an unpublished iconographic and epigraphic programme, as well as possible marks of use and manufacture. The poor state of conservation of the original surface made it impossible to visualise the details as a whole, so we applied photogrammetric methods, and subsequently processed models using various GIS analysis and point cloud processing softwares.Two photogrammetric models (in Agisoft PhotoScan) were made to document the trap in general: one prior to the conservation and restoration process; and a second three-dimensional (3D) model once the surface had been cleaned. The purpose of the second model was to visualise the reliefs programme in general, as well as the different surface details. The first complete 3D model of the object was used to perform a virtual reconstruction of the anchor including the elements that did not preserve, using a 3D modelling program (Blender).Nine areas of the stock surface were selected for the analyses of the various iconographic and epigraphic features, which were documented and processed in Agisoft PhotoScan. The Digital Elevation Model (DEM) and point cloud models were then processed with different analyses tools in Geographic Information System (GIS) (such as QGIS) and point cloud processing software (CloudCompare). Our results document a piece of highly interesting information from its surface consisting of reliefs of four dolphins; at least four rectangular stamps: two of them with possible inscriptions, and an anthropomorphic figure. Thanks to the comparative data, we conclude that the four dolphins were made with the same stamp during the stock manufacturing process. Further, we were able to reconstruct the dolphin stamp, partially preserved in each of the reliefs, by unifying the 3D models, thus revealing the original set. This system of stamping by means of reusable dies is well known in other elements such as amphorae but has not been studied in the specific case of lead traps.In the case of the epigraphic elements, the 3D documentation methodology revealed numerous micro-surface details, not visible under conventional documentation techniques, which could help specialists to interpret these inscriptions. Although they have not been analysed in this research, its documentation has promoted the appreciation of surface details that could refer to the manufacturing processes (moulds and tools) or the traces of use, providing historical information on this object. At the same time, the virtual reconstruction of the anchor has aided the formation of hypotheses on the dimensions and original appearance of the anchor. The different tools used, such as raster analysis using shadow mapping and point cloud alignment, proved to be very effective. They have fulfilled the established objectives and have helped to establish a possible analysis methodology for future lead traps with decorative elements. These types of artefacts recovered from underwater sites are very common in museum collections. In many cases, their state of conservation and the difficulty in handling them due to their size and weight make it difficult to document surface details. In this case, the multidisciplinary work of conservation and 3D documentation allows for high-quality documentation that is easy to access and exchange between researchers. The combined use of photogrammetric techniques with virtual RTI provides a non-invasive method for the object, low cost and easy processing compared to other conventional methods.

Новые находки скоплений петроглифов на Канозере (период 2017–2019).

For the period 2017–2019 five new groups of petroglyphs and a significant number of previously unknown ones in already documented panels of petroglyphs were revealed on the rocky islands of the Kanozero Lake. The discovery of petroglyphs was facilitated by the use of photogrammetric techniques, as well as careful night photographing of rocks with petroglyphs. This publication presents findings of five new panels with more than 40 petroglyphs in total. These findings expand our ideas about the stylistic diversity of the Kanozero petroglyphs, about the range of heights above level of the lake on which stylistically close petroglyphs were made. In this work, new motifs and compositions of rock carvings are introduced, both having analogues and previously nottypical of Kanozero.

Assessment of UAV-based digital surface model and the effects of quantity and distribution of ground control points

ABSTRACT The development of unmanned aerial vehicles (UAVs) along with that of positioning and imaging sensors has promoted the use of photogrammetric techniques for applications other than the conventional acquisition of the Earth’s surface information. Moreover, the accuracy of photogrammetric products depends on several parameters, such as sensor quality and stability, image scale, strip overlap, and the number and distribution of ground control points (GCPs). Although technological developments have improved the automation and accuracy of the photogrammetric process, the acquisition of GCPs remains a highly time-consuming task. To address this problem, this study investigated the positional error of digital surface models (DSMs) generated via the post-processing of data acquired with a SenseFly eBee Classic, with respect to the number and distribution of GCPs. A single flight was conducted over a test field located at an urban expansion region of Presidente Prudente, State of São Paulo, Brazil. Nine DSMs were generated using different configurations of the number and distribution of GCPs. An accuracy assessment was performed based on 20 horizontal check points and 270 vertical check points determined by global navigation satellite system (GNSS) positioning. The vertical error surfaces were generated by Kriging. The Student’s t-test, Chi-square test, and root mean square error (RMSE) were used for the positional accuracy assessment. The results show that the qualities of the products generated by GNSS-supported Aerial Triangulation (GNSS-AT) without GCPs were in accordance with those indicated by the UAV manufacturer. In contrast, the results obtained by considering the GNSS-AT with different GCPs were not in accordance with the manufacturer’s claims. Finally, RMSE values of approximately 3 ground sample distance (GSD) for the horizontal component and 5 GSD for the vertical component are achievable with at least three well-distributed GCPs; however, the use of additional points is encouraged.

Grain Size Distribution of Copper Ore as Means for Qualitative Evaluation of Its Lithological Composition

Information about the grain size distribution of a material plays an important role in optimizing production systems in various branches of industry. Analysis of particle size distribution in the run-of-mine material is frequently employed to verify the quality of drilling and blasting operations. Adequate software and improved grain size identification technologies not only help to monitor and evaluate the results of blasting operations, but also inform the selection of blasting methods which best correspond to particular geological and mining conditions both in surface mining and in underground mining. The accuracy of indirect, image-analysis methods used in the identification of grain size distribution motivated some pilot works aimed at using the grain size to evaluate the quality of a lithological complex copper ore deposit. Describing the run-of-mine material fed to the Ore Enrichment Plant (OEP) with the use of its grain size distribution may improve the techniques currently employed to optimize the energy efficiency of ore treatment processes. A model of ore flow in the underground transportation system, developed in the FlexSim environment, as part of the DISIRE research project, may prove a valuable optimization tool. This paper presents the results of preliminary research aimed at verifying whether grain size distribution of the run-of-mine material correlates with its lithological composition. The examinations covered grain size distribution in copper ore transported on belt conveyors in two mines in which the extracted ore has different lithology. The research was performed with the use of photogrammetric techniques and the Split Desktop 4.0 computer application. The advantage of the proposed technique is that it can be used at any location in the mine. The analysis was performed on the photographic material collected in situ at the “Lubin” mine. This material was supplemented with qualitative data stored in the Run-Of-Mine Ore Monitoring system (further: MOPRONA), as defined on the basis of channel samples collected on the day of tests.

GIS and three-dimensional modeling for cultural heritages

Cultural heritages are the history of the nations, and history forms the identities of the nations. Therefore, protection of cultural heritages means protection of the history and identity of the nations. Identification of the current status of cultural heritages is important for documentation, preservation, and for use as a base for restoration. Documentation studies need robust and scientific methods. GIS and photogrammetry have recently been the most commonly used scientific methods for documenting cultural heritages. The aim of this study is investigate the photogrammetric method and GIS for documentation of cultural heritages digitally. In documentation studies, digital terrestrial photogrammetry is one of the main methods of processing information of historical monuments on computers according to GIS and documenting it in three dimensions. In this study for documentation, all data of 46 historical monuments located in Silifke/Mersin were collected and transferred to a database so that it is made queryable. Some of those heritages were reconstructed as 3D models by the use of photogrammetric techniques. Finally, 3D Models were integrated into the system for presentation.

Ethnic–based Photodocumentation of Nasofacial Angle: The Anioma Study

ABSTRACT Context: Human morphological variations, along with its attendant physiologic sequalae, have long been noted by physical anthropometrists to follow a combination of genetic and environmental factors. Anthropometric variation in angular craniometric norms, including the nasofacial angle, is not exempted from the influence of these factors. Aim: This craniometric study was aimed at evaluating variation extant in obtained nasofacial angle among a sample population of adult Anioma subjects. Methods and Materials: Participants’ degree of nasofacial angle variation was measured in a cross section of one thousand (1000) Anioma indigenes by the use of photogrammetric techniques. Results: Obtained results showed that sampled Anioma male subjects presented a mean nasofacial angle of 37.86º±3.22, with minimum and maximum values of 32.00º and 48.00º in the order given. Selected female participants showed a mean angle of 36.30º±3.89, which on statistical analysis, proved to be significantly different from obtained male values. Conclusion: Research findings herein support the gender specific nature of nasofacial angle in the study population, thereby suggesting its forensic significance as a basis for subject identification, among others.

Concurrent validity of photogrammetric and inclinometric techniques based on assessment of anteroposterior spinal curvatures

PurposeThe purpose of the study was to investigate correlations between parameters of anteroposterior spinal curvatures in the sagittal plane, measured with the use of photogrammetric technique and inclinometer in healthy elderly women.MethodsRandomized study involved 50 females, ranging from 50 to 70 years of age (mean 62.26 ± 6.94); mean body mass index (BMI) 27.69 ± 4.79. The examined parameters included angle of inclination in lumbosacral spine (ALFA), thoracolumbar transition (BETA), upper thoracic segment (GAMMA), angle of lumbar lordosis (LLA) and thoracic kyphosis (TKA). Results obtained with gravitational inclinometer were compared with those identified with photogrammetry method. Statistical analyses were performed with Mann–Whitney U test, regression analysis and Bland–Altman analysis.ResultsIn Mann–Whitney U test, with correction due to continuity, no statistically significant differences for any variable were found. Regression analysis was significant only for the variable of BETA angle. Bland–Altman coefficient for the respective angles was: ALFA 2.0%, BETA 4%, GAMMA 0%, LLA 2% and TKA 0%.ConclusionsThe results acquired with gravitational inclinometer and with photogrammetric technique are comparable, as the parameters of anteroposterior spinal curvatures acquired with these two methods are found to be compatible in the case of measurements of lumbar lordosis and thoracic kyphosis.

Utility of Large Scale Photogrammetric Techniques for 3-D Mapping and Precision Iron Ore Mining in Open Pit Areas

Precision mining and optimization of ore mining practise are gaining more importance as the global demand and competition for exploring the raw mineral material has grown manifold with increased industrialization world-wide. The overall process of mining activity involves ore identification, estimation, planning, excavation, transportation etc. The activity requires accurate mapping, monitoring and proper management of information pertaining to ore stockpile, mining pits and infrastructure of the areas on a regular basis. Of late, advancements in remote sensing techniques have paved a way for digital management of the mining activity. Especially, use of photogrammetric techniques for open pit mining are found to be highly accurate and effective in capturing, monitoring, mapping, managing the information pertaining to mining in a three dimensional (3D) space. Capturing of information pertaining to mines in 3-D perspective with respect to a specific location on the terrain is highly effective in accurate estimation of ore reserves, exploration and reclamation planning, ore continuity mapping and decision making. However, precision mining requires the use of large scale photogrammetric techniques with high resolution imagery of gigabytes size at mapping scales range from 1: 1000 to 1: 5000. In addition to that, the entire procedure involves the use of state-of-theart software and hardware for fast processing of data and subsequent digital output generation. Above all, involvement of skilled photogrammetric experts with specialised knowledge on open pit mining is very much essential for accurate interpretation and delineation of the resources. A project was carried out for the 3D mapping of iron ore stockpiles, pits and infrastructure areas at various sites. The stockpile and pit mapping is used for very precise volume measurements and the infrastructure mapping is used for general mine planning activities. High accuracy is critical, as the data and volume reports are used to calculate the value of the ore being extracted, and any errors in the mapping data can result in incorrect payments of large amounts of money. Since, the timeline specified to complete the task is very short, it is crucial that the staff doing the final volume computations and downstream processing should receive the accurate data, correctly coded and mapped according to the standards outlined. The study has demonstrated a typical workflow for the effective use of close range photogrammetric techniques for 3D mapping and iron ore mining in open pit areas. The study also sees a brighter outlook and challenges of upcoming aerial and terrestrial photogrammetric technology for precision mining.

Photogrammetric, Geometrical, and Numerical Strategies to Evaluate Initial and Current Conditions in Historical Constructions: A Test Case in the Church of San Lorenzo (Zamora, Spain)

Identifying and quantifying the potential causes of damages to a construction and evaluating its current stability have become an imperative task in today’s world. However, the existence of variables, unknown conditions and a complex geometry hinder such work, by hampering the numerical results that simulate its behavior. Of the mentioned variables, the following can be highlighted: (i) the lack of historical information; (ii) the mechanical properties of the material; (iii) the initial geometry and (iv) the interaction with other structures. Within the field of remote sensors, the laser scanner and photogrammetric systems have become especially valuable for construction analysis. Such sensors are capable of providing highly accurate and dense geometrical data with which to assess a building’s condition. It is also remarkable, that the latter provide valuable radiometric data with which to identify the properties of the materials, and also evaluate and monitor crack patterns. Motivated by this, the present article investigates the potential offered by the combined use of photogrammetric techniques (DIC and SfM), as well as geometrical (NURBs and Hausdorff distance) and numerical strategies (FEM) to assess the origin of the damage (through an estimation of the initial conditions) and give an evaluation of the current stability (considering the deformation and the damage).

Stereo-Orthoimage as a GIS Tool for Reliable Restitution of Cultural Monuments

The use of photogrammetric techniques for the geometric documentation of monuments and archaeological sites is widely known and applied. The basic techniques are: (a) the stereo-restitution, which provides the advantage of 3D observation and accurate digitization but requires specific photogrammetric knowledge and equipment, and (b) the orthophoto, an easy to use raster product that enables the 2D digitization, which is, however, not sufficient for monuments that consist of complex surfaces. The concept of stereo-orthoimage was firstly introduced at the end of the 1960s for cartographic and cadastral applications, combining the advantages of both the orthophoto and 3D observation. This paper analyses the algorithms used for the generation of stereo-orthoimages, presents a developed plugin for the free open-source Geographic Information System QGIS that implements the stereo-orthoimage technique and examines the use of this technique for the restitution and digitization of complex surfaces of monuments for their large scale geometric documentation. The QGIS plugin, named OrthoStereoMate (OSM), has been developed in the Python programming language and will become freely available to the official python plugin repository for QGIS users.

Rock slope stability analysis using photogrammetric data and DFN–DEM modelling

Structural and mechanical analyses of rock mass are key components for rock slope stability assessment. The complementary use of photogrammetric techniques and numerical models coupling discrete fracture networks with the discrete element method (DEM) provides a methodology that can be applied to assess the mechanical behaviour of realistic three-dimensional (3D) configurations for which fracture persistence cannot be assumed. A real case has been studied to show the complete methodology from the acquisition of the photogrammetric data to the numerical modelling of the potential progressive failure process occurring in the rock mass. Using a 3D mapping system and its associated structural mapping tool Sirovision, the topography and the discontinuity set of an unstable rock block located in a limestone layer of the Mount N,ron, located in the French Alps, were imported into a DEM code specially enhanced for the modelling of pre-fractured rock masses. A stability analysis has been carried out, emphasizing the contribution of rock bridge failure through a mixed shear-tensile failure process to the generation of new failure surfaces. This addresses limitations in methodologies using only shear strength reduction method. It is believed that the proposed methodology can strengthen the basis for a more comprehensive stability analysis of complex fractured rock slopes.

Combining photogrammetry and photographic enhancement techniques for the recording of megalithic art in north-west Iberia

Photogrammetry is an indirect technique that allows one to obtain different recording products – orthophotographs, planimetries, 3D models, etc. – that are essential for the study of prehistoric rock art. We believe nonetheless that there is no single technique capable of effectively registering an entire rock art site, so it is highly recommended to use a combination of several systems – that is to say, the development of a specific recording methodology – in order to obtain a documentation which is as thorough as possible. In this regard, different possibilities of combination of photogrammetry with other photographic techniques have been analysed, with the aim of obtaining an accurate recording of the art and its support, seeking also to incorporate into this recording other essential data for the study of its state of preservation.The use of photogrammetric techniques will be described, along with the tests carried out with photographic techniques such as polarised light photography or those that register images at both ends of the visible spectrum, both in the ultraviolet (UV) and in the infrared region (IR). These techniques enable the revelation of invisible details to clarify issues concerning technology and to explore scarcely noticeable forms of alteration. In some cases, these experiences have been complemented by the use of laser scanning in order to compare the effectiveness of both techniques.With all the experience acquired, it is possible to propose a rather precise recording methodology that requires no specialised technical training and no complex equipment.

Faulting and fissuring in active oceanic rift: Surface expression, distribution and tectonic–volcanic interaction in the Thingvellir Fissure Swarm, Iceland

Iceland brings exceptional opportunity for analysing extension related to rifting of the Mid-Atlantic ridge, especially revealing fresh structural patterns in active fissure swarms. Post-glacial fracture systems of the Thingvellir rift segment of the West Volcanic Zone (WVZ) and interaction with holocene lava flow overlapping are analysed in detail in this paper. We mapped 5390 fractures at metric to kilometric scales in order to realise a precise structural map, a representative fault length distribution analysis and some statistical calculations in terms of fault length/number growth rates from Holocene to recent time. Mapping and 3-D geometrical analysis of faults and fissures are based on use of photogrammetric techniques, GPS positioning at ground control points and validation from geological field work. This approach allowed us to measure the vertical throw distribution along 52 faults with a precision around 0.5–1 m. Most of these faults have symmetric serrated fault-displacement profiles; however some of them have profiles offset to the north or south. Fault vertical offset as a function of the age of the hosting lava flows are presented too. Finally, from the study of 70 transverse topographic profiles and the fault offset analysis, we propose a propagation model for Holocene fissure development, partly controlled by Pleistocene tectonic inheritance. Our model takes into special account alternating volcanic events and faulting. Simple fissure zones with small hangingwall monocline or more complex scarp zones with graben and larger hangingwall monocline developed. Because of lava flow accumulation during the rift extension, estimating the amount of extension based on the present-day morphology would have led to severe under-evaluation.

Scanning electron microscope study of pore systems in rocks

Pore systems in rocks are generally affected by grain size, shape, sorting, packing, nature of cementing materials, by detrital and authigenic pore fillers, and by the previously imposed pressure and temperature history. These variables, through their influence on the pore structure, control important petrophysical properties such as porosity, permeability, irreducible fluid saturation, formation resistivity factor, specific surface area, and velocities and attenuations of elastic waves. By presentation of photomicrographs, the scanning electron microscope (SEM), with its large depth of focus and magnification, is shown to reveal details of pore spaces of rocks in three dimensions. The pore systems of 42 rock samples, obtained from surface outcrops and during the drilling of oil wells, were examined. In most cases, the details of the pore structure would not have been possible to study under a light transmission microscope. SEM micrograph sequences of typical pore structures from the more extensive study were selected and are presented for one sandstone, one limestone, one dolomite, five shale, and two granite samples. It is suggested that maps of pore structures in rocks could be quantitatively obtained from overlapping stereo pairs of micrographs through use of photogrammetric techniques.

Photogrammetry Aids in Pipeline Location Surveys

Use of photogrammetric techniques in determining most economical route for pipe lines; by photo interpretation studies, maps showing 5 ft contours at scale of 1 in. to 200 ft or smaller can be prepared in areas where selection of route will be affected by topographic conditions; use of topographic relief displacement techniques.

Aerophotogrammetry applied to the survey of large areas at mean scale

Technical maps of scales varying from 1/100 to 1/10,000 may differ considerably one from another in their typical features. Consequently, the economy in the use of photogrammetric techniques in place of classical ground methods can only be established for each particular case. The references given here are to cadastral maps of large areas, and in this case it is proposed to show that photogrammetric methods are preferable from an economic point of view. If we compare the normal processes of this type of work executed by ground survey methods with the corresponding photogrammetric methods itis obvious that some of the processes are common to both methods, and that there are equivalent phases, such as, for example, “ground survey and small details plus land sketches plus geometric construction of the map” which are analogous to “flying plus plotting”. In order to illustrate the economies of the problem, the cost of the ground survey must be compared with the plotting performance which the air survey plotting instrument must produce. Eventually, it will be shown that the performance of the plotting instrument may or may not reach the desired efficiency. In 1934, the Italian Cadastre entrusted the photogrammetric production of the first cadastral maps to private enterprise, with the proviso that the cost should not exceed the estimated cost of the classical ground methods. The commercial undertakings accepted this condition, thus substantiating in some degree that the cost of the photogrammetric mapping of this type can be economically undertaken. Recently, in both Italy and Portugal there has been further competition in private enterprise for surveys on a scale of 1/1000, 1/2000 and 1/5000 in which the companies could make use of both ground and air survey methods. The result of the contracts accepted once again of both the higher economy of the photogrammetric method. Average costs for such surveys over large areas under the specification comparable to those of the Italian Cadastro are:

Aerophotogrammetry applied to the survey of large areas at mean scale

Summary 1) Technical maps of scales varying from 1/100 to 1/10,000 may differ considerably one from another in their typical features. Consequently, the economy in the use of photogrammetric techniques in place of classical ground methods can only be established for each particular case. The references given here are to cadastral maps of large areas, and in this case it is proposed to show that photogrammetric methods are preferable from an economic point of view. 1) The original article has been published in Italian in Photogrammetria, 1949–1950, no. 4. If we compare the normal processes of this type of work executed by ground survey methods with the corresponding photogrammetric methods itis obvious that some of the processes are common to both methods, and that there are equivalent phases, such as, for example, “ground survey and small details plus land sketches plus geometric construction of the map” which are analogous to “flying plus plotting”. In order to illustrate the economies of the problem, the cost of the ground survey must be compared with the plotting performance which the air survey plotting instrument must produce. Eventually, it will be shown that the performance of the plotting instrument may or may not reach the desired efficiency. In 1934, the Italian Cadastre entrusted the photogrammetric production of the first cadastral maps to private enterprise, with the proviso that the cost should not exceed the estimated cost of the classical ground methods. The commercial undertakings accepted this condition, thus substantiating in some degree that the cost of the photogrammetric mapping of this type can be economically undertaken. Recently, in both Italy and Portugal there has been further competition in private enterprise for surveys on a scale of 1/1000, 1/2000 and 1/5000 in which the companies could make use of both ground and air survey methods. The result of the contracts accepted once again of both the higher economy of the photogrammetric method. Average costs for such surveys over large areas under the specification comparable to those of the Italian Cadastro are: