Glossary

ASP and stereo photogrammetry vocabulary, with links to the deeper concept pages.

ASP

Ames Stereo Pipeline. NASA’s open-source stereo photogrammetry toolkit. Docs.

asp_plot

The Python visualization companion to ASP. Reads ASP output files and produces diagnostic plots + PDF reports. Docs.

ATL06-SR

ICESat-2 Land Ice Height (sliderule edition) — the canonical Earth-altimetry product used for DEM alignment. Fetched on the fly via SlideRule.

base-to-height ratio (B/H)

Ratio of inter-satellite baseline to satellite altitude. Larger B/H = better height precision; typical 0.3–0.6 for Earth-orbiting satellites.

bundle adjustment

Joint optimization of camera parameters and 3D tie-point positions to minimize reprojection error. ASP tool: bundle_adjust. See Bundle adjustment.

CCD artifact

Sub-pixel discontinuity at the boundary between adjacent CCD chips on push-broom sensors. WorldView-1 and -2 exhibit this; corrected by wv_correct. WorldView-3 does not.

convergence angle

Angle between the two viewing directions of a stereo pair at the ground point. Sweet spot for natural terrain: 15–30°.

Copernicus DEM (COP30)

Globally-available 30 m DEM, openly distributed on AWS Open Data. Default reference DEM for Earth tutorials.

CSM

Community Sensor Model. A pluggable camera-model standard ASP can use as an alternative to RPC for some sensors. Used in jitter-correction workflows.

disparity map

Per-pixel (x, y) shift between matched pixels in a stereo pair. ASP file: *-F.tif.

DEM

Digital Elevation Model. A regular grid of heights — the final product of an ASP run. ASP file: *-DEM.tif.

dh

“Difference in height”. Pixel-wise difference between two DEMs (or between a DEM and altimetry).

geodiff

ASP tool that computes the difference between two DEMs and reports statistics.

ground sample distance (GSD)

Pixel size of imagery on the ground, in meters. WV3 pan-sharp GSD ≈ 0.30 m; ASTER GSD ≈ 15 m.

ICESat-2

NASA’s Ice, Cloud, and Land Elevation Satellite 2. Provides global laser altimetry used for DEM alignment.

interest point (IP)

Distinctive corner or blob detected in an image, used as a candidate feature for matching across images.

jitter

High-frequency satellite attitude variation that violates the rigid-camera assumption of standard sensor models. ASP corrects via jitter_solve (CSM cameras only).

LOLA

Lunar Orbiter Laser Altimeter. Reference altimetry for Moon DEMs.

match file

ASP file containing tie-point matches between two images. File extension .match (binary) or .csv.

MOLA

Mars Orbiter Laser Altimeter. Reference altimetry for Mars DEMs.

NMAD

Normalized Median Absolute Deviation — robust scale estimator. 1.4826 × median(|x - median(x)|). Equals std for normal distributions; resistant to outliers. Used everywhere asp_plot reports DEM error.

NTF

NITF (National Imagery Transmission Format). Image format used by some commercial sensors.

orthorectification

Resampling input imagery onto a regular geographic grid using a coarse reference DEM. Makes stereo matching dramatically easier. ASP’s tool for this is mapproject, and ASP docs call the step “mapprojection”. See Orthorectification.

parallax

Apparent shift of a pixel between two images of the same ground point taken from different viewpoints. Encodes the height of the ground point.

pc_align

ASP tool for ICP-based registration of point clouds. Used to align a DEM to ground-truth altimetry. See Alignment.

point cloud

Unstructured 3D points produced by stereo triangulation. ASP file: *-PC.tif (encoded as a GeoTIFF for compactness).

point2dem

ASP tool that grids a point cloud into a regular DEM.

reprojection error

Distance, in pixels, between an observed image feature and the predicted position of its 3D ground point reprojected through the camera model. Bundle adjustment minimizes this.

residual

Per-tie-point reprojection error. asp_plot.bundle_adjust plots these before and after bundle adjustment.

RPC

Rational Polynomial Coefficients. Compact parametric camera model used by most commercial Earth-observation satellites.

SfM

Structure from Motion. The general algorithmic family that bundle adjustment + stereo belongs to.

SGM / MGM

Semi-Global Matching / Modified Global Matching. The stereo-correlation algorithms ASP uses to produce highest quality results (asp_sgm, asp_mgm).

SlideRule

Cloud-native API for on-demand ICESat-2 processing. asp_plot uses it to fetch ATL06-SR data.

SpaceNet

Open dataset of high-resolution commercial satellite imagery, hosted on AWS. The UCSD WV3 scenes used in this guide come from the SpaceNet CORE3D collection.

stereo

ASP’s master command for stereo correlation + triangulation. The parallel version (parallel_stereo) is what tutorials actually use.

subpixel mode

Setting that controls how parallel_stereo refines integer-pixel matches; e.g. mode 9 (Bayes EM with MGM).

tie point

A single 3D ground point observed (and matched) in two or more images. Bundle adjustment optimizes camera parameters using tie-point reprojection errors.

WorldView

DigitalGlobe / Vantor high-resolution Earth-observation satellite series (WV1, WV2, WV3, WV4). All push-broom; all use RPC camera models.