I have some cpc precipitation data stored in IMG format.
Could anyone suggest a software beside ERDAS imagine or Arcgis which can be freely downloaded?
GDAL supports .img format, both the basic Imagine and the extended Imagine (greater than 2GB), thus any software that utilizes GDAL drivers would support ERDAS Imagine.
The most workable and well documented that I have seen is QGIS. It is also open source and therefore free.
The software to choose depends on your objectives.
For GIS purpose, QGIS is great. It includes many toolboxes for spatial analysis. It is an open source alternative to ArcGIS.
For image processing, you can use Monteverdi. Monteverdi is particularly usefull if you have very large images. It is an open source alternative to Erdas.
If you are looking for a free software there are several that can do that however I don't know how can they handle the CPC imagine files but ENVI 5.1 can open it and can read img files if that is what you are looking for. ENVI is not free but is another good software to have around. I have ERDAS, ArcGIS 10.1 and ENVI 5.0 and they all can open and read it. Not sure if the free software have the capability to handle CPC file.