When launching GRASS GIS for the first time, you will open a default Location "world_latlog_wgs84" where you can find a map layer called "country_boundaries" showing a world map in the WGS84 coordinate system.
![[GRASS GIS after first startup]](grass_start.png) 
The main component of the Data tab is the Data Catalog
which shows the GRASS GIS hierarchical structure consisting of
Database ![[GRASS Database]](grassdb.png) ,
Location
,
Location ![[Location]](location.png) and
Mapset
 and
Mapset ![[Mapset]](mapset.png) .
.
![[GRASS Database]](grassdb.png) GRASS Database (directory with projects)
 GRASS Database (directory with projects)![[Location]](location.png) Location (a project)
 Location (a project)![[Mapset]](mapset.png) Mapset (a subproject)
 Mapset (a subproject)For more info about data hierarchy, see GRASS GIS Database page.
First, if you would like to get to know GRASS better before importing your own data,
please download provided samples such as the "North Carolina" dataset.
You can simply reach them through
"Download sample location to current database" management icon
![[Download Location]](location-download.png) .
.
To work with your own data, you typically want to first create a new Location
with a 
coordinate reference system (CRS) suitable for your study area or one that
matches your data's CRS. The Location Wizard ![[Add Location]](location-add.png) will help you with that by guiding you through a series of dialogs to browse
and select predefined projections (also via EPSG code) or to define individual
projections.
will help you with that by guiding you through a series of dialogs to browse
and select predefined projections (also via EPSG code) or to define individual
projections.
If you know the CRS of your data or study area, you can fill EPSG code or description and Location Wizard finds appropriate CRS from a predefined list of projections. If you do not know CRS of you data, you can read it from your georeferenced data file (e.g. shapefile or GeoTiff file with the related metadata properly included).
![[Raster import]](raster-import.png) ,
,
![[Vector import]](vector-import.png) or a variety of more specialized tools.
If the data's CRS does not match your Location's CRS, data will be automatically reprojected.
After import your raster or vector data are added as a layer to Map Display.
To change layer properties, go to Display tab.
To analyze your data, search for a tool in the Modules tab.
 or a variety of more specialized tools.
If the data's CRS does not match your Location's CRS, data will be automatically reprojected.
After import your raster or vector data are added as a layer to Map Display.
To change layer properties, go to Display tab.
To analyze your data, search for a tool in the Modules tab.
List of EPSG codes (Database of worldwide coordinate systems)