GRASS FAQ

This pages contains a growing list of Frequently Asked Questions (FAQs). Feel free to add text, "Edit" button for that. See also Category: FAQ for more articles.

Usage

1. In a site map, how to select all the points that are at the edge? - Points Edge Selection
2. How to create a buffer around polygons using v.buffer? - Vector Buffer
3. What are LOCATIONs and MAPSETs? - Location and Mapsets
4. Starting GRASS - Starting GRASS
5. How to see if you can use GRASS for anything at all - Grass Assess
6. ERROR: Default region not set - Error Region
7. Nothing shows in monitor window - Region Map
8. How to show labels, such as street labels on a vector map? - Labels Show
9. What is a raster MASK? - GRASS Raster Mask
10. What is an attribute? - GRASS Attributes
11. Is is possible to switch from one LOCATION to another while running GRASS? - Switch Locations
12. Changing region during operation? - Changing Region
13. Point in polygon test: - Point in Polygon
14. Georeferencing an image?
15. How do I reproject a raster or vector map? - Map Reprojection
16. How do I enjoy high quality statistic analysis in GRASS? GRASS and Rstat
17. What is the difference between pseudo-topological and real topological vect formats? - Topo Issue
18. How to to aggregate values from one polygon layer to another ? - Aggregate Values
19. How to diplay a vector (polygon) map colored by the attributes in a particular column? Vector Attribute Display
20. How to Convert vector types
21. How to Dissolve polygons

Data

1. Can I map data from an arbitrary database model to work with GRASS without having to restructure or create a new database?
2. How can I drop columns in a sqlite-database? - Sqlite Drop Column

Technical

1. GRASS 6 symbols - [README]
2. GRASS 5.7 vector architecture - Vector Faq GRASS57
3. Does GRASS57 installation override my stable GRASS5x installation? GRASS5x and 57
4. Are GRASS 5.0.x/5.3.x/5.4.x raster maps compatible with GRASS57? Yes!
5. How do I compile/install GRASS57? Compile and Install

Installation

GRASS 6 compilation problems

1. Can't find a library even after I've built and installed it: Make sure that /usr/local/lib (or where you installed it) is listed in your /etc/ld.so.conf file and (as root) run /sbin/ldconfig.
2. grass 5.7 compilation problems: - GRASS57 Compilation
3. grass 5.3, 5.4 compilation problems: - GRASS53 Compilation
4. How do I install grass in windows 2000: - WinGRASS Installation

GRASS and Cygwin

1. How do I find the Cygwin packages to install? - Cygwin Packages
2. I can't find pq.dll: Make sure you installed the PostgreSQL package in the Cygwin [installer].
3. I can't find pq.dll: try copy cygpq.dll to pq.dll

Errors

1. In a Latitude-Longitude location I'm getting the error Illegal latitude for North when importing an unprojected raster image: Unprojected images are given a resolution of 1 pixel per line, and so any image with a height of more than 90 pixels will try and write data to an impossible latitude.
   Solution: import the image into a simple XY location and georeference the image with either r.region (if bounds are simple and known) or i.points and i.rectify. An automated alternative to r.region is to create a "World File" to be used by r.in.gdal. See the GeoTIFF format help page at [[1]].