The orthophotography process begins with digital imagery. Photographs are taken with high resolution cameras pointing straight down. Images are taken at intervals to ensure significant overlapping of the images. The cameras record and store GPS positional information within the image file. Powerful software then analyzes the images and finds similar items that are common in multiple images. When an object is located in several images, it’s location can be triangulated from the camera GPS positions. When this is done on dozens of photos and thousands of pixels. The software then merges images to obtain an accurate, seamless orthometric aerial map that has been corrected so that distance measured on the map accurately reflects the true distance on the ground. Where high order mapping measurements are not required, orthophotos are also available at lesser accuracies without the need to install ground control points.
Without accurate ground control, aerial mapping can be very helpful, but measurements from them are not reliable. However, when corrected using high accuracy ground control points, accuracy increase substantially. Surveyors can expect accuracy’s of 1-2 inches horizontal and 2-3 inches vertically. Control Points can be set before or after the UAV flight. Check Points of the same precision are used to verify the final product and report overall processing accuracy.
Orthomosaics and 3D models can be delivered in several formats. Our software generates output files that can be used and manipulated in popular CAD and GIS programs such as AutoCAD, Microstation, ArcGIS and others. 3D point cloud models can be produced and delivered in CAD format. Other files that can be delivered are shape files of contours, csv file of dtm grid points, tiled tif’s for large projects. The geo-referenced aerial maps can have sub-centimeter resolution. Files can be downloaded or delivered on USB flash drive.
ADVANTAGES FOR LAND SURVEYORS
High Resolution Aerial Imagery - 4K video and 12 MP photos. Mapping resolution up to ½ inches per pixels shows details as small as pavement cracks.
Accurate Mapping and Contours - 1-2 inch horizontal and 2-3 inch vertical accuracy with Ground Control Points. Higher accuracy than most conventional aircraft acquired mapping.
Fast Acquisition and Delivery - Turn-around from request to delivery often complete within a few days.
Certifiable Date of Acquisition - In contrast to the unknown dates of Internet based aerial imagery, mapping and photos are taken on a specific date.