Seeking Open Source alternatives to ArcGIS Aggregate and Extract Value to Points?

Question

I am looking for some kind of Open source GIS library which can perform spatial analytic functions same as ArcGIS.

My use case is : I am processing GeoTIFF file provided by USGS and performing Aggregate and Extract Values to Points functions from ArcGIS. Once I have result in GeoDatabase I create Text File out of that, that's all I do. Instead of using Aggregate and Extract Value to Points function from ArcGIS I want to use some open source.

Any thought?

Answer 1

1. Extracting values at points:
   
   In GRASS you can use v.sample and can acces this through QGIS. Alternatively you can use the Point Sampling plugin (Plugins->Fetch Python Plugins).
2. Aggregate:
   GRASS has many raster functions which will allow you to achieve what you want, though there isn't a directly analogous one to aggregate. Which one you choose will rather depend on how you want to aggregate your data. Alternatively, you could use GDAL_grid to interpolate from your old raster to a new raster.