Double-precision Geocoding Specification
Target release | 2.0 |
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Epic | |
Document status | DRAFT |
Document owner | @Former user (Deleted) |
Designer | |
Developers | |
QA |
Goals
The following Java interfaces and classes currently operate on 32-bit floats: GeoCoding, GeoPos, PixelPos. Derived classes such as TiePointGeoCoding also perform their computations using 32-bit floats, while others, e.g. PixelGeoCoding use 64-bit internally.
Many hires applications require 64-bit precision both for internal computation and in the final delivery of results.
Background and strategic fit
With S1TBX, this is a problem for high res TerraSAR-X data. In particular when running the SAR Simulation it produces a number of artifacts in the image.
Before
After
Assumptions
Requirements
# | Title | User Story | Importance | Notes |
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1 | Tie point interpolation | Part of the problem is caused by the unit (lat lon in degrees, slant range time in seconds) but this should probably stay as is. At high resolutions (< 1m), neighbouring pixels end up having the same value. Tie Point Grids and DEMs need to be interpolated to the resolution of the data product. Interpolators have already been made 64-bit. Now the resulting value needs to be saved as 64-bit.
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2 | Tie point writing/reading | When writing tie point grids a datatype field specifies if it is Float32 or Float64 When reading, the reader should use this field to first determine the type and then read the data accordingly |
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3 | Readers | All readers which create TPGs in particular for storing lat and lon data shall be changed to supprt Float64 |
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4 | Interfaces | Access to tie point grids for the purpose of coordinate positions should be via getPixelDouble or getPixels(double[]) |
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User interaction and design
Questions
Below is a list of questions to be addressed as a result of this requirements document:
Question | Outcome |
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