#mrsid

For the last two days at work my co-worker and I have been wrestling with ArcMap and ArcPad (on a Juno 3B Trimble) trying to just get a TIFF to display with some shapefiles. When we loaded in the TIFF it didn’t show up, so we thought maybe it was a size thing so we converted the file to a MrSID. Still nothing. Also the extension for .tif was toggled ON in the Advanced Settings. 

We did a bunch of tests in ArcMap (projections etc) and STILL NOTHING. 

Finally, today, she had the epiphany that the problem was in the numbers, literally. ArcPad 8 only displays 8-bit files, and our TIFFs were 16-bit. So we converted the file down and BAM it showed up. 

MrSIDs! Do you know what these are? They have their place in the GIS world. 

If you don’t feel like reading too much, MrSID is a file format that compresses large georeferenced raster images, and they are popular especially with government agencies that release imagery for the public to download.

I did a post before about how to download free orthoimagery from the USDA’s Geospatial DataGateway here, but I didn’t go too into detail with how to work with a MrSID download.

Basically, it’s a file format created for downloading and opening large aerial images. Lizardtech makes software called Lizardtech Geoexpress that you can use to easily manipulate MrSIDs ( .sid is the file format extension) to the extents you need, and it will keep the images georeferenced, and it can also convert MrSIDs into other formats such as JPEGs, TIFFs, or PNGs with an optional World File, which will georeference those file formats so you can also use them in GIS.

According to its Wikipedia page:

Most commercial GIS software packages can read some versions of MrSID files including those from GE Smallworld, ESRI, Intergraph, Bentley Systems, MapInfo, Safe Software, Autodesk, with ERDAS IMAGINE being able to both read and write MrSID files.

So there you have it. I didn’t encounter this file type until after college, but I ended up using them a lot with environmental work. If you’re doing work that involves downloading aerial imagery, this is something you definitely need to know about.

Examples of GIS data sites that use MrSIDs:

GeoSpatialDataGateway

NH’s GRANIT

NJDEP’s GIS Digital Download Page

Have a great weekend! Guillermo and I just got offered a community garden plot in Columbia, so we will be busy getting our green thumbs ready. 8^D