Mr. Sid Who?
Which image file format is best for my mapping project?
At the MapWarehouse checkout, you'll need to choose a format for the files you've added to your cart before your order can be delivered. JPG and MrSID are the most popular compressed image formats. Both formats can be read by most up-to-date CAD and GIS software. The best file format to use for your particular project depends on what you're planning to do with the imagery layer.
JPG is a fine option where the goal is simply to view the imagery across as many platforms as possible and use it as a base layer to give context to your vector files. MrSID is the preferred choice where more demanding image manipulation or analysis will be involved and the resulting output needs to retain the data quality characteristics of the original.
Related: The Essential Cheat Sheet For Purchasing Digital Geo Data
JPG offers a reasonable balance between file size and image quality, and is most useful for images with smooth transitions between tone and colour. For this reason, JPG is easily the most popular format in digital photography and can be used with countless types of software. It does not hold up well to image processing or multiple edits, however, and can tend to lose detail of colour variation, causing a blocky appearance after decompression and recompression (posterization). FBS offers georeferenced JPG imagery by using an auxiliary *.WLD world file, which references the the coordinates where the image tile should be inserted in the map, read by geo-capable software.
MrSID (multiresolution seamless image database) is a technology owned by LizardTech specifically for use with georeferenced imagery like orthophoto, which could have up to 8 - 16bit multispectral bands. The file size can be compressed up to 20:1 without degrading the image’s appearance for RGB. Using MrSID format therefore allows very large files to be viewed quickly without the need to fully decompress the image. Furthermore, metadata like pixel resolution is inherent in the image and is updated automatically during processing.
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