Supported Geospatial File Formats
By Sandra Schloen, October 2014
Updated May 2017
OCHRE supports shapefiles (.shp and associated sidecar files), certain geodatabase formats, along with a variety of raster image types including jpg, tif, png, and GeoTIFF formats.
Raster image files can be very large. Since these are typically being delivered over the web it is important not to create image files that are larger than necessary. The extent and resolution of an image determines the degree to which OCHRE can pan and zoom on the image so these factors need to be carefully considered, and weighed against their impact on the file size.
Before georeferencing an image for use in OCHRE, crop out any unnecessary information around the edges. That is, be intentional about not including unnecessary content. Then review the Strategies for Creating Raster Images to ensure that your image options are well chosen.
Supported Rasters
See the ArcGIS documentation for a list of supported raster types.
TIF format
Probably the most common format for a georeferenced raster image is the .tif format. These are well supported by the OCHRE GEO features. A georeferenced tif has a collection of sidecar files that accompany the main <filename>.tif file. OCHRE only needs to have the tif file itself be added as an OCHRE Resource item; it already understands this format and will use the accompanying sidecar files appropriate. Here is a typical example of a full set of files for a single georeferenced tif file.
TIF file with sidecar files
A typical TIF file may be huge in size. Since many of our images will be deployed over the web it is best to devise a strategy for creating files that makes them as compact as possible without sacrificing resolution. See below for some strategies and options to consider when scanning, georeferencing and preparing tif files.
GeoTIFF format
A georeferenced tif can be saved in ArcMap (e.g. version 10) using the File, Export Map, Save as tif, with the Write World File option checked on. This will create a supplementary side-car file with the .tfw extension that must accompany the original tif file in the same folder.
Alternatively, in ArcMap create a new map that has just a single tif file as a layer. Use File, Export Map, check on the Write GeoTIFF tags option and set the Compression to None. This GeoTIFF format is essentially a stand-alone format, not requiring additional world files.
JPG format
It is also possible to use georeferenced JPG file within GEOchre. To save a file from ArcMap in JPEG format to use in OCHRE, with the appropriate layer selected use File, Export Map (General), with the Write World File option checked on. For the Format choose the Color Mode of 8-bit Grayscale. Alternatively, right-click on the layer that represents the tif file. Use the Data option to Export Data ... and select JPG as the export Format.