The emergence of different airborne sensors for geospatial data capture has allowed working with different methodologies in cartographic production. For this reason, it is necessary to study the feasibility of the modern technologies and their operative development in order to achieve the optimized integration of geospatial data.
Every technological advance is an essential step to fulfill the needs of society, at the same time being important that the technicians responsible indicate the means of improving results in consideration of the different user capabilities. In this process the national cartographic institutions must give their professional advice and establish the working patterns normalizing the cartographic production criteria, so as to honour the purpose demanded by society.
The current potential in cartographic production for information registration depends on the choice of passive sensors such as analogical cameras and matrix or linear array digital cameras; active sensors such as LIDAR and RADAR; information sources such as RGB, Panchromatic, near IR, intensity level, position (x, y) and height first echo ... last echo); sensor orientation through INS/GPS and/or aerotriangulation; advantage out of the information (cartography, DTM, DSM, etc.) through photogrammetric techniques, LIDAR or RADAR.
In short, the production framework will depend on the available means and on the technical specifications set up for carrying out the work. We should take into account that the above-mentioned options – in addition to the traditional ones – allow the integration of information from the different sensors and its subsequent management in order to achieve the intended objective. This will be the subject of this paper along with decision taking and the pertinent quality control, as well as the exploitation of the information through the detection of changes and vectorization.
PHOTOGRAMMETRY VS LIDAR
|Sensor type||Punctual||Matrix or linear|
|Measurement of points||Direct without redundancy. Accuracy of information only depends on calibration of system components||Indirect with redundancy. Images with overlay provide the intersection of the homologous rays (HR)|
|Information type||Punctual. Reconstructed surface (type of material and observed structure) difficult to assess||May be punctual, lineal or superficial. Easy to interpret reconstructed model due to info source: the image|
|Sampling||Individual points||Full areas|
|Associated image||None or monochromatic image||High geometric and radiometric quality|
|Horizontal accuracy||2-5 x less than vertical accuracy||1-3 x better than vertical accuracy|
|Vertical accuracy||10-15 cm (~ 10 cm per 1,000 m on heights of 2,500 m)||Depends on flight altitude and focal length of the camera|
|Flight plan||More complete. Small passes. higher potential for data||Needs consideration of longitudinal and transverse coverage|
|Flight constraints||Less impact of time, daylight, night, season clouds||Daylight flying, clean atmosphere necessary|
|Production range||May be automated, thus a greater production||Higher need of editing control|
|Budget||25%-33% of budget: photogrammetric compilation|
|Production||Software: depends on qualified commercial & technical people||Software for the end-user: slow process of identification and manual extraction. Not reliable if automated, implies editing, especially at large scales.|
|Data acquisition limited by a largely contrasted area||Data can be acquired. Successfully used in coastal cartographic production||Difficult and expensive|
|Feature extraction||Definition of zones or areas||Edge limits 2-D|
|Results||Edges or limits 3-D||Edges and zones 3-D|