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The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-2/W2, 2016 11th 3D Geoinfo Conference, 20–21 October 2016, Athens, Greece
UAV PHOTOGRAMMETRY IMPLEMENTATION TO ENHANCE LAND SURVEYING, COMPARISONS AND POSSIBILITIES
a, b a a a R. El Meouche *, I. Hijazi , PA Poncet , M. Abunemeh , M. Rezoug
a Université Paris-Est, Institut de Recherche en Constructibilité, ESTP-Paris, F-94230, Cachan, France b An-Najah National University, Nablus, Palestine *firstname.lastname@example.org
Commission VI, WG VI/4 KEY WORDS: Land Surveying, UAV, Photogrammetry, Point Cloud, 3D Model.
The use of Unmanned Aerial Vehicles (UAVs) for surveying is now widespread and operational for several applications – quarry monitoring, archeological site surveys, forest management and 3D modeling for buildings, for instance. UAV is increasingly used by land surveyors especially for those kinds of projects. It is still ambiguous whether UAV can be applicable for smaller sites and property division. Therefore, the objective of this research is to extract a vectorized plan utilizing a UAV for a small site and investigate the possibility of an official land surveyor exploiting and certificating it. To do that, two plans were created, one using a UAV and another utilizing classical land surveyor instruments (Total Station). A comparison was conducted between the two plans to evaluate the accuracy of the UAV technique compared to the classical one. Moreover, other parameters were also considered such as execution time and the surface covered. The main problems associated with using a UAV are the level of precision and the visualization of the whole area. The results indicated that the precision is quite satisfactory with a maximum error of 1.0 cm on ground control points, and 4 cm for the rest of the model. On the other hand, the results showed that it is not possible to represent the whole area of interest utilizing a UAV, due to vegetation.
Land surveying is one of the oldest professions on earth. The purpose of many surveys nowadays is to create a 2D plan that a land surveyor and his client could use to obtain a building permit. Innovation in topography and land surveying is aimed at acquiring more data with higher accuracy. Computer developments were a key change in that regard. Nowadays, utilizing drones could lead to another quantum leap in the surveying profession. With the development of smart cities and BIM technologies, it will probably become easy to create a 3D model of a terrain utilizing UAVs and exporting it to a 3D Geographic Information System (GIS). Up until now, for construction sites, 2D plans have been required to get reliable measurements quickly.
Topographic plans are widely used in a variety of applications and at various sites. These plans involve several levels of accuracy depending on the client’s needs. Usually, projects that require crucial safety conditioning for construction, such as high-speed railways, landing strips, investigating building deformations or tunnel inspections, require plans with high accuracy, where just a few millimeters (mm) of deformation are highly significant.
In some countries land surveyors’ signature has a legal value. Their tasks involve ensuring the accuracy of a plan and making sure that the landmarks are assigned to the right place. Actually, they use topographic instruments in order to realize the plans. This involves a broad number of applications from private properties to major public infrastructures, roads and network management, for instance.
For many topographical surveys, the data are acquired with a total station. A total station is surveying equipment that consists of an electromagnetic measuring instrument and
electronic theodolite. It is also integrated with a microprocessor, electronic data collector and storage system. The instrument can be used to measure horizontal and vertical angles as well as the slope distance from the object to the instrument. The redundant measures with total stations allow accuracy to within millimeters to be achieved. Furthermore, their automatic operation enables more data to be acquired in a limited period of time. Over one day a land surveyor can acquire up to 2,000 points. Since the process is repetitive it can easily involve errors.
Therefore several techniques can be adopted to avoid, or at least minimize, these possible errors. For instance, the French government set specific legislation on precision classes for topographical surveys in order to control the quality of the data. The Arrêté du 16 septembre 2003 establishes a set of equations and values to confirm that topographical surveys comply with a designed class of precision.
The survey then has to be georeferenced using different techniques based on the nature of the terrain and the available instruments. Usually, the most efficient technique used is a global navigation satellite system (GNSS) receiver with a real-time kinematic (RTK) network. This allows control points to be obtained with a precision of about 2.0 cm.
Once the field survey is completed, the data are transferred to CAD software to generate the plan. Even though codification in the field enables automatic drawing, it usually involves some errors, and the post-treatment process usually takes several hours to obtain the final product.
In France, the land property is registered in a document called a “cadastre” (land register). This was first established in the 19th century in the reign of Napoleon. The evolution of topographic instruments and progress in terms of precision revealed that most of the register was inaccurate. Therefore,
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This contribution has been peer-reviewed. doi:10.5194/isprs-archives-XLII-2-W2-107-2016 107
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