The Automatic Terrain Generation (ATG) module in SOCET GXP provides fully automated capabilities to extract elevation data from stereo imagery.
The intuitive interface provides user friendly options for creating accurate, high-resolution digital terrain models (DTM). ATG allows users to generate SOCET GXP® Grid, DTED, NITF, and GeoTIFF files natively in SOCET GXP, reducing editing and production time, while eliminating the need to import and export files.
Automatic Terrain Generation (ATG) consists of functionality from:
- Automatic Terrain Extraction (ATE)
- Next-Generation Automatic Terrain Extraction (NGATE).
Both ATE and NGATE are used to generate digital terrain models (DTM). The DTM is needed to create digital photogrammetric products such as orthophotos, perspective scenes, and image maps. The main difference between ATE and NGATE is that NGATE generates a more accurate and dense DTM.
NGATE and ATE – which one should I use?
Both NGATE and ATE are used to create digital terrain models (DTM). In SOCET GXP the output format of the DTM is a grid, which is a two-dimensional array of elevation points called posts. The array of posts is always aligned north, south, east, and west with the coordinate system.
NGATE is significantly different from ATE. ATE performs image correlation on each post. NGATE performs image correlation and edge-matching on each image pixel. Users control ATE speed by using a large post spacing to reduce the number of posts. NGATE speed is not dependent on post spacing or number of posts. Users control NGATE speed by stopping NGATE at a different minification level using different Precision/Speed options.
The most significant advantage of using NGATE over ATE is for difficult areas such as large-scale imagery in urban areas. ATE is not effective for distinguishing buildings from the ground. Therefore, the DTM climbs up over building roofs. NGATE DTM quality in those difficult areas is far better than those from ATE. As a result, NGATE can significantly reduce DTM editing time.
In terms of DTM accuracy, NGATE almost always produces more accurate DTMs than ATE. If speed is important to DTM production, users should set the NGATE Precision/Speed option to Medium/Medium. With this setting, NGATE can generate a DTM faster than ATE with slightly better accuracy. If the desired product is an accurate and dense DTM, NGATE always performs better than ATE.