OBJECTIVE OF THE SERVICES
Eletrosul hired Esteio to execute LIDAR Aerial Surveys to generate Digital Elevation Model (DEM) point clouds, Digital Terrain Model (DTM) point clouds, one meter interval Contour Lines and Hypsometric Maps, for an area of 276 square kilometers within the municipality of Santana do Livramento, state of Rio Grande do Sul.
LOCATION
Service area is within the municipality of Santana do Livramento, state of Rio Grande do Sul – Brazil, close to the border with Uruguay.
FLIGHT PLAN
During planning activity, Esteio made a detailed LIDAR flight plan for the area, based on a graphic file containing the area boundaries provided by Eletrosul.
Esteio made the flight plan in order to obtain products compatible to the service requirements. The LIDAR flight plan includes coordinates for starting and closing flight strip points, distance between the flight strip axes and flight height.
FLIGHT EXECUTION
The flight occurred according to favorable atmospheric conditions, during three days in April 2011.
The flight crew worked together with the survey team, as this one occupied a reference base station during the LIDAR flights using a GPS equipment.
The flight crew used as base the Airport of Santa Maria, state of Rio Grande do Sul.
PLACEMENT OF GEODETIC SURVEY MARKS
In order to serve as departure for future topographic surveys, survey team placed two pairs of geodetic survey marks inside the area, two main stations and closed to each one, an azimuth mark. These survey marks were also used as base reference for GPS Survey during LIDAR survey procedures.
Esteio used geodetic survey marks of IBGE (national geodetic authority) as origin to the geodetic survey marks placed in the area, as well as benchmarks of IBGE, from an existing leveling line close to the area.
LIDAR PROCESSING AND DTM
After finishing LIDAR surveys, Esteio performed LIDAR data raw processing, which included equipment calibration parameters, information about relief and vegetation type, and equipment configuration.
For DTM classification, Esteio used TerraScan LiDAR Data Processing Package, separating ground points from above-ground points according to geometric distribution, elevation and laser pulse return intensity.
LIDAR-GENERATED COMPOSITION IMAGE
After LIDAR processing and classification, Esteio produced the Lidar-generated composition images, which are hipsometric images aggregated to intensity values of each Lidar point.
Each hipsometric image has a color scale starting with blue, used to indicate lower elevation points, and finishing with red, which indicates higher elevation points.
CONTOUR LINES
From the Digital Terrain Model (DTM), Esteio generated one meter interval contour lines, being five meters for index contour lines. Esteio also defined elevation points in highest and lowest locations, as well as over longest flat areas.
FINAL MAPS
Over the Lidar-Generated Composition Images Esteio printed the contours lines, thus generating the final maps.
Esteio delivered three different map collections, according to the needs of Eletrosul, one containing the images, other containing vectors only and another with both, images and vectors.