Problem: Datasets do not line up when added to ArcMap
After adding several datasets to an ArcMap Data Frame, features in some layers do not align correctly with other layers.
When adding data to ArcMap, the application reads the coordinate system (projection) information stored with the dataset. When displaying multiple datasets with different coordinate systems, ArcMap will project the data 'on-the-fly' to the coordinate system that is set for the Data Frame:
• If there is no coordinate system associated with the data, or
• If the coordinate system definition is incorrect, or
• If the proper geographic (datum) transformation is not specified,
the data will not line up properly with other data displayed in the map document.
Solution or Workaround
The following are suggestions for troubleshooting the cause of data alignment problems in ArcMap.
- Go to View > Data Frame Properties > Coordinate System tab, and verify that a Current Coordinate System is set for the Data Frame.
The coordinate system of the Data Frame is adopted from the first data added to the new Data Frame. If that data does not have a defined coordinate system, the map's coordinate system will be set to 'Unknown', and subsequent data added to the map cannot be projected on the fly.
- Determine if the dataset has a coordinate system assigned to it.
Right-click on the name of the layer in the Table of Contents, select Properties > Source tab, and examine the contents of the Data Source box for the coordinate system definition.
- If there is no coordinate system defined, review the metadata in ArcCatalog, or additional documentation that may have been delivered with the data.
The coordinate system parameters that need to be obtained are:
Units of measure (Decimal degrees, feet, meters)
Zone (UTM coordinate system)
Zone or Fipszone (State Plane coordinate system)
geographic coordinate system (Datum)
Some coordinate systems may require additional parameters such as:
1st standard parallel
2nd standard parallel
Latitude of origin
False easting value and units
False northing value and units
- If a coordinate system definition does exist for the data, it is possible that the definition is incorrect.
- For further information, and suggestions on how to resolve these issues, refer to the Esri Knowledge Base articles in the Related Information section below. The article entitled 'Identify the spatial reference, projection, or coordinate system of data' at the link below is especially useful for data that has no coordinate system defined, or to identify the correct coordinate system for data.
- Apply a geographic (datum) transformation in ArcMap
- Select the correct geographic (datum) transformation when projecting between datums
- Align vector data in ArcMap
- How to define the projection for ArcGIS data
- Identify the spatial reference, projection, or coordinate system of data
- Projection Basics: What the GIS professional needs to know