You are here:
- Support Home >
- Knowledge Base >
- Technical Articles >
- Article Detail
Index: How to define the projection for ArcGIS data
| Article ID: | 24175 |
|---|---|
| Software: | ArcGIS - ArcEditor 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2, 9.3 ArcGIS - ArcInfo 8.0.1, 8.0.2, 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2, 9.3 ArcGIS - ArcView 8.1, 8.1.2, 8.2, 8.3, 9.0, 9.1, 9.2, 9.3 |
| Platforms: | N/A |
Summary
Defining the projection for a data set is a very important part of working in ArcGIS. Although it is possible to work with data that has an undefined projection, it is not possible to properly overlay data from different projections without first defining a projection. Additionally, certain analysis tools can be inaccurate with data that does not have a projection defined.
Defining a projection is different from projecting data. Defining a projection simply attaches the information ArcGIS needs to properly display and geoprocess the data. Defining a projection for a data set does NOT modify the coordinates of the data.
The method for defining the projection for ArcGIS data varies by data type, for example: Geodatabase, coverage, and shapefile.
When referring to ArcGIS, the terms coordinate system and projection are often used interchangeably. In actuality, it is important to define a coordinate system for your data. A coordinate system can, but does not always, include projection information.
To define a coordinate systems/projection for your data, read the following topics specific to the data type.
Defining a projection is different from projecting data. Defining a projection simply attaches the information ArcGIS needs to properly display and geoprocess the data. Defining a projection for a data set does NOT modify the coordinates of the data.
The method for defining the projection for ArcGIS data varies by data type, for example: Geodatabase, coverage, and shapefile.
When referring to ArcGIS, the terms coordinate system and projection are often used interchangeably. In actuality, it is important to define a coordinate system for your data. A coordinate system can, but does not always, include projection information.To define a coordinate systems/projection for your data, read the following topics specific to the data type.
Topics
- Define a projection for a shapefile to a predefined coordinate system
To reproject a shapefile, the shapefile must have a projection defined. You can use ArcToolbox to define a shapefile's projection. - Define a coordinate system interactively for a coverage
To define a projection for a coverage, you can select a map projection and specify its parameters interactively using ArcToolBox. - Define a custom projection for a geodatabase
This article describes how to define a custom projection for a geodatabase using ArcToolBox. - Define a coordinate system interactively for a coverage using ArcCatalog
To define a projection for a coverage, select a map projection and specify its parameters interactively using ArcCatalog.
Created: 1/2/2003
Last Modified: 9/17/2008