---
name: "v.proj"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/v.proj"
---

# v.proj(1grass)

Re-projects a vector map from one project to the current project.

## NAME

**v.proj**  - Re-projects a vector map from one project to the current project.

## KEYWORDS

vector, projection, transformation, import

## SYNOPSIS

**v.proj**\
 **v.proj --help**\
 **v.proj** \[-**lzwb**\] **project**=*name*  \[**mapset**=*name*\]   \[**input**=*name*\]   \[**dbase**=*path*\]   \[**smax**=*float*\]   \[**output**=*name*\]   \[**pipeline**=*string*\]   \[--**overwrite**\]  \[--**help**\]  \[--**verbose**\]  \[--**quiet**\]  \[--**ui**\]

### Flags:

- **-l**

  List vector maps in input mapset and exit

- **-z**

  Assume z coordinate is ellipsoidal height and transform if possible\
   3D vector maps only

- **-w**

  Disable wrapping to -180,180 for latlon output\
   Latlon output only, default is -180,180

- **-b**

  Do not build vector topology\
   Recommended for massive point projection

- **--overwrite**

  Allow output files to overwrite existing files

- **--help**

  Print usage summary

- **--verbose**

  Verbose module output

- **--quiet**

  Quiet module output

- **--ui**

  Force launching GUI dialog

### Parameters:

- **project**=*name* **\[required\]**

  Project (location) containing input vector map\
   Project name (not path to project)

- **mapset**=*name*

  Mapset containing input vector map\
   Default: name of current mapset

- **input**=*name*

  Name of input vector map to re-project

- **dbase**=*path*

  Path to GRASS database of input project\
   Default: path to the current GRASS GIS database

- **smax**=*float*

  Maximum segment length in meters in output vector map\
   Increases accuracy of reprojected shapes, disable with smax=0\
   Default: *10000*

- **output**=*name*

  Name for output vector map (default: input)

- **pipeline**=*string*

  PROJ pipeline for coordinate transformation

## DESCRIPTION

*v.proj* allows a user to convert a vector map in a specified mapset of a specified project (different from current) with coordinate reference system (CRS) of source project to the vector map in a current mapset of current project with CRS of current project (both CRSs are defined in their corresponding projects). The CRS information can be viewed and managed with *g.proj*.

For an introduction to map CRSs (and the PROJ library), see the manual page of r.proj.

## NOTES

If **output** is not specified it is set to be the same as input map name.\
 If **mapset** is not specified, its name is assumed to be the same as the current mapset’s name.\
 If **dbase** is not specified it is assumed to be the current database. The user only has to specify **dbase** if the source project is stored in another separate GRASS database.\
 If **smax** is set to **0** the automated vertex densification is disabled (not recommended).

*v.proj* supports general datum transformations, making use of the *PROJ* co-ordinate system translation library.

When projecting into a latlon project, east coordinates are wrapped by the proj4 library to fit into the range -180,180. This is in most cases appropriate, but can cause errors the input vector crosses the datum line at 180E/W. In this case wrapping of east coordinates to -180,180 needs to be disabled with the **-w** flag.

When reprojecting massive point clouds for which topology is not necessary, the user can set the **-b** flag to suppress the building of topology of the output map.

In order to preserve spatial detail, *v.proj* performs automated vertex densification (as an alternative, *v.split* could be used before reprojecting. Without vertex densification, depending on the source and target CRS (Coordinate Reference System), geometries can be substantially deformed (straight lines become curves, squares become trapezoids, etc). The densification of linear features can help to avoid topological errors.

## EXAMPLE

Reprojection of a vector map from another project (and mapset) into the current mapset:\

```
v.proj in=mymap project=latlong mapset=user1
```

## REFERENCES

-

  - **1**

  Evenden, G.I.  (1990) Cartographic projection procedures for the UNIX environment - a user’s manual. USGS Open-File Report 90-284 (OF90-284.pdf) See also there: Interim Report and 2nd Interim Report on Release 4, Evenden 1994).

- **2**

  Richards, John A. (1993), Remote Sensing Digital Image Analysis, Springer-Verlag, Berlin, 2nd edition.

PROJ: Projection/datum support library.

**Further reading**

- •

  ASPRS Grids and Datum

- •

  Projections Transform List (PROJ)

- •

  Coordinate operations by PROJ (projections, conversions, transformations, pipeline operator)

- •

  MapRef - The Collection of Map Projections and Reference Systems for Europe

- •

  Information and Service System for European Coordinate Reference Systems - CRS

## SEE ALSO

*g.proj,* *m.proj,* *r.proj,* *i.rectify,* *r.stats,* *v.sample,* *v.split,* *v.surf.idw,* *v.surf.rst*

## AUTHORS

Irina Kosinovsky, US ARMY CERL\
 M.L. Holko, USDA, SCS, NHQ-CGIS\
 R.L. Glenn, USDA, SCS, NHQ-CGIS

## SOURCE CODE

Available at: v.proj source code (history)

Accessed: Monday Feb 24 17:51:17 2025

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.1 Reference Manual