Pipeline overview#
Every ASP run, regardless of sensor, follows the same five-stage pattern.
The five stages#
Sensor prep → bundle adjustment → orthorectification → stereo + DEM generation → alignment. The dashed stages are optional: the simplest possible run is parallel_stereo followed by point2dem, and each optional stage buys accuracy at the cost of another step. The tutorials show both: the ASTER notebook starts with the minimal run, then adds orthorectification; the WorldView notebooks add alignment and bundle adjustment.
Stage 1: Sensor preparation#
Vendor-specific tools (aster2asp, wv_correct, cam2map, dg_mosaic) convert raw vendor data into the standard image-plus-camera pair ASP expects.
Stage 2: Bundle adjustment#
bundle_adjust refines the vendor camera models by minimizing reprojection errors of features matched between the input images. See Bundle adjustment.
Stage 3: Orthorectification#
mapproject resamples each input image onto a reference DEM grid so stereo matching has only a small remaining disparity to solve. See Orthorectification.
Note
ASP calls this step “mapprojection” in its toolchain (mapproject, --mapproj-dem). This guide uses “orthorectification” — the more standard photogrammetry term — for the concept while keeping ASP’s tool names verbatim.
Stage 4: Stereo + DEM generation#
parallel_stereo matches pixels between the two images and triangulates them into a point cloud; point2dem grids the cloud into a regular DEM. The heights are of whatever surface the cameras saw, rooftops and tree canopy included, so the product is strictly a digital surface model (DSM); this guide follows ASP in calling it a DEM. From the WorldView tutorial, the disparity map and the DEM it becomes:
Stage 5: Alignment#
pc_align registers the DEM to a trusted reference (ICESat-2, MOLA, LOLA, or another DEM) using ICP. See Alignment.
What asp-plot does at every stage#
Each ASP stage produces files; asp-plot reads them and produces diagnostic plots and PDF reports. See Visualization.