|Version 6 (modified by qliu, 12 months ago)|
PostGIS Raster SoC Idea 2012 - Distance Analysis Tools for PostGIS Raster
Student: Qing Liu
Mentor: Pierre Racine
The idea for this proposed project is to add two spatial analysis functions to PostGIS Raster that implement two main ways of performing distance analysis: Euclidean distance calculation and cost-weighted distance calculation.
Euclidean distance function will create a distance surface representing the Euclidean distance from each cell in the source layer to the starting point or the closest source (as designated by user). The basic concepts of the algorithm would be using the center of the source cell to calculate the distance from it to the rest cells in the raster layer or within the user-defined extent.
Cost-weighted distance will create a raster layer representing the accumulative cost distance for each cell to the starting point or the closest source (as designated by user). A cost raster layer will be generated using one or several factor layers representing the impedance of passing through each cell according to user’s criteria. User can also put weights on the input factor layers to represent different levels of importance for those factors. Factors such as: elevation, slope, orientation, land use / land cover type; vehicle speed, accessibility; and a binary map layer could also be used as a mask for defining geographic extent or as a filter for the output cost layer. The accumulative cost values will be then assigned to each cell representing the cost per unit distance for moving through this cell.
GSoC 2012 Proposal:
Week 1 Report
What did you get done this week?
- Compiled PostGIS 2.0 sucessfully.
- Loaded raster data into PostgreSQL and practiced some query by finishing the raster/vector tutorial.
- Wrote an analysis of how Euclidean distance and Cost-weighted distance are computed in ArcGIS and GRASS.
- Setup wiki page.
What do you plan on doing next week?
- Learn more about PostGIS Raster concepts and functions
- Write an analysis of how Euclidean distance and Cost-weighted distance are computed in Oracle
- Start to write a proposal on how to adopt the concepts and algorithms in PostGIS.
Are you blocked on anything?
- As of now I was not blocked on anything yet, but working in a spatial database is something new and challenging to me. I will need to read and reserch more about it.
- However, it took me some time to understand how raster coverage is stored in PostGIS, and how Raster type works.