A GeoTIFF is a standard format for storing georeferenced raster data. It is based on the Tagged Image File Format (TIFF) and allows geospatial information like map projections and coordinate systems to be embedded in the image file. Exporting data into a GeoTIFF is a common task in GIS software and allows the raster data to be used in other programs that support the format. This article will provide a step-by-step guide on how to export a GeoTIFF using different GIS applications.
What is a GeoTIFF?
A GeoTIFF is an image file format used to store georeferenced raster datasets. It is based on the TIFF format but has additional metadata tags that allow coordinate system, map projection, ellipsoid and other spatial reference information to be embedded in the image file. This extra information allows the image to be correctly positioned and scaled when viewed in GIS software. Some key advantages of the GeoTIFF format include:
- Wide support across many GIS and image processing software packages
- Allows georeferencing information to be embedded in the file
- Supports various raster data types like multispectral, thematic or continuous data
- Lossless compression to reduce file sizes
- Open format that is well documented
Due to these benefits, GeoTIFF is one of the most widely used formats for storing and exchanging geospatial raster data between different GIS, remote sensing and other imaging applications.
Why Export as a GeoTIFF?
There are several reasons you may want to export raster data as a GeoTIFF file:
- To make the data compatible with other GIS software
- To maintain the georeferencing information with the raster
- To reduce file sizes using lossless GeoTIFF compression
- To share or distribute the raster dataset to others
- For long term archiving of spatial data
- To upload the data to online repositories or services
- To modify or process the data in other image editing programs
By exporting as a GeoTIFF, the raster can be easily integrated into new workflows and environments while retaining its spatial reference properties. This avoids having to re-georeference the data later.
Exporting a GeoTIFF in QGIS
QGIS is a popular open source GIS software. To export a GeoTIFF in QGIS, follow these steps:
- Load the raster layer you want to export into QGIS
- Right click the layer and select ‘Export’ > ‘Save As…’
- In the Save Raster Layer as dialog, choose GeoTIFF as the Format
- Select the CRS (coordinate reference system) for the output GeoTIFF
- Set additional options like the raster extent or resolution
- Choose the file location and name for the GeoTIFF output
- Click Save to export the layer to a GeoTIFF file
The exported GeoTIFF will contain all the spatial reference information and metadata from the original raster layer. You can control options like compression, pyramid resampling, and more during the export process.
Exporting a GeoTIFF in ArcGIS
In ArcGIS, exporting a raster dataset to a GeoTIFF can be done using the Copy Raster tool:
- In ArcMap/ArcCatalog, navigate to the raster layer you want to export
- Right click the layer and select Data > Export Data
- In the Export Raster Data dialog, select the output location and name
- Set Format to TIFF
- Enable the Write GeoTIFF Tags option
- Configure any other export settings and click Save
This will run the Copy Raster geoprocessing tool to convert the raster to a GeoTIFF with all spatial reference metadata. You can also use the Save As option from the layer right-click menu in ArcMap to export a GeoTIFF.
Exporting a GeoTIFF in QGIS
In QGIS, exporting a GeoTIFF is straightforward using the Save As option:
- Load the raster layer to export into your QGIS project
- Right click on the layer and select Export > Save As…
- In the Save Raster Layer as dialog, choose GeoTIFF as the format
- Select the desired CRS, extent, resolution, and other settings
- Enter a file path and name for the output GeoTIFF
- Click Save to export the raster to a GeoTIFF file
This will create a new GeoTIFF containing all the spatial reference system information and metadata from the original raster layer. You can customize options like compression and pyramid resampling during export.
Exporting a GeoTIFF in MapInfo Pro
To export a raster as a GeoTIFF in MapInfo Pro:
- Open the raster layer you want to export
- Click TAB > Export
- Choose TIFF/GeoTIFF as the export format
- Select a file location and name for the GeoTIFF output
- Enable the Generate GeoTIFF export option
- Configure other settings like pixel depth and click OK
This will convert the raster to a GeoTIFF while retaining georeferencing data like the coordinate system definition. The bit depth, nodata value and other attributes can be configured during export.
Exporting a GeoTIFF in ERDAS IMAGINE
In ERDAS IMAGINE, the Export wizard can be used to convert a raster to GeoTIFF format:
- Open the raster layer for export in the View window
- Click File > Export Data
- Select TIFF/GeoTIFF as the output format
- Choose an output folder location and filename
- Set any reprojection, resampling, or GCP options
- Enable the Generate GeoTIFF Tags option
- Click Finish to run the export
This will export the raster to a GeoTIFF while preserving all georeferencing information including map projection parameters, coordinate system, and GCPs if applied. Advanced options like compression and overviews can also be configured.
GeoTIFF Export Options
When exporting a GeoTIFF, there are a few key options to consider for the output file:
- Projection/Coordinate System – The target geographic or projected CRS for the GeoTIFF.
- Extent – The geographic area or bounding box to include in the export.
- Resolution – The pixel size or raster resolution to use.
- Compression – Lossless compression like LZW or JPEG to reduce file size.
- Pyramids – Resampled overviews for faster display at reduced resolutions.
- NoData Value – Pixel value to use for nodata areas without valid data.
Choosing appropriate settings for the intended use of the GeoTIFF can optimize it for analysis or display in other applications. Compression, tiling, and overviews can significantly improve performance when working with large raster datasets.
GeoTIFF Metadata
A key advantage of the GeoTIFF format is the ability to embed geospatial metadata within the file itself. This metadata may include:
- Projection information like EPSG code, well-known text, or PROJ string
- Georeferencing details such as model tie points, RPC coefficients
- Coordinate system definitions including datums and ellipsoids
- Bounding coordinates of the raster’s extent
- Pixel size and scale
- Origin and orientation of the raster grid
Storing this metadata directly in the GeoTIFF allows the file to stand alone with all reference information required to georegister it on import into other software. The open format specification supports inclusion of a wide range of geospatial metadata content.
Uses of GeoTIFF Files
GeoTIFF is a versatile format used across many GIS and geospatial applications. Some common uses cases include:
- Storing and transferring geospatial raster datasets
- Exchanging data between GIS systems and software
- Making rasters available for web mapping and analytics
- Releasing scientific multispectral/hyperspectral remote sensing data
- Archiving historical map and aerial imagery data
- Publishing raster products like DEMs or thematic maps
The format is widely supported by desktop GIS, image processing tools, web mapping engines, metadata catalogs, and spatial databases. This interoperability makes GeoTIFF an effective standard for handling raster geospatial data across many domains.
Advantages of GeoTIFF Files
Some of the key advantages of using GeoTIFF files include:
- Wide support across virtually all GIS software
- Contains georeferencing metadata within the file
- Lossless compression options to reduce file sizes
- Open format with public specifications
- Can store coordinate system information and projections
- Supports large file sizes and high resolution imagery
- Can integrate with spatial databases and web services
By leveraging these capabilities, GeoTIFF provides an interoperable container for handling geospatial raster data across different workflows and environments.
Conclusion
Exporting raster data to a GeoTIFF format enables the raster to be used with many other GIS and imaging software packages. It provides a standardized way of embedding georeferencing metadata within the file itself, avoiding lost spatial reference information when transferring datasets between systems. Modern GIS programs offer streamlined export options to convert data to GeoTIFF while retaining key attributes like the coordinate system, pixel size, nodata values and compression settings.
Understanding when and how to export a GeoTIFF facilitates better interoperability and sharing of raster geospatial data between systems. The format has become an industry standard for handling georeferenced imagery and gridded datasets across desktop, web, mobile and cloud platforms. Taking advantage of the capabilities of GeoTIFFs ultimately makes raster data easier to work with in a variety of GIS workflows and use cases.