View Source

Target release	2.0
Epic
Document status
Document owner	Former user (Deleted)
Designer	Lead designer
Developers	Lead developer
QA	Lead tester

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.

SNAP > Double-precision Geocoding Specification > TSX-1.png

Before

SNAP > Double-precision Geocoding Specification > TSX-2.png

After

Assumptions

List the assumptions you have such as user, technical or other business assumptions. (e.g. users will primarily access this feature from a tablet).

Requirements

#	Title	User Story	Importance	Notes
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.	Must Have	Additional considerations or noteworthy references (links, issues)
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	Must Have
3	Readers	All readers which create TPGs in particular for storing lat and lon data shall be changed to supprt Float64
4	Interfaces	Access to tie point grids for the purpose of coordinate positions should be via getPixelDouble or getPixels(double[])

User interaction and design

Include any mockups, diagrams or visual designs relating to these requirements.

Questions

Below is a list of questions to be addressed as a result of this requirements document:

Question	Outcome
(e.g. How we make users more aware of this feature?)	Communicate the decision reached

Not Doing

List the features discussed which are out of scope or might be revisited in a later release.