bmcgaughey1 / USGSlidar

A collection of functions to browse lidar data collections, query collections for coverage for specific locations, and retrieve data covering locations.
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Using web mercator in FIAPlotExample.R script #9

Closed bmcgaughey1 closed 2 years ago

bmcgaughey1 commented 2 years ago

There are substantial distortions associated with the web mercator projection for CONUS. This means that samples defined to be a specific size in the web mercator projection will be a very different size in a projection that has less distortion of distances and areas. The example builds PDAL pipelines to clip 1000m square areas. In reality, the actual sample areas will be much smaller. A simple work-around is to call prepareTargetData with data in a projection with less distortion to do the buffering of point locations. However, selection of a suitable projection to use for CONUS is problematic. UTM is an option but this will involve multiple zones for some/most states. Albers equal area conic is another option but this introduces rotation in the sample areas that may necessitate a larger sample size to ensure coverage for areas around a plot locations. Changing to a 1400m square would ensure coverage 1000m around a plot but this doubles the sample area and will result in longer retrieval times and larger point and derived output files.