The next set of MLI Data that I find tremendously useful is the MLI Digital Imagery. These are orthophotos of most of the province.
An orthophoto or orthophotograph is an aerial photograph geometrically corrected (“orthorectified”) such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances, because it is an accurate representation of the earth’s surface, having been adjusted for topographic relief[1], lens distortion, and camera tilt. Wikipedia
In essence, orthophos are airphotos that have been tweaked so that they can be used as a map.
From MLI
Here’s an photo showing the land near Tone Ag. In order to cut the photo down to a reasonable size I shrank it. It is no longer georeferenced and therefore no longer an orthophoto.
Mostly I use the 5Km Tiles – MrSid. MrSid is an image format like the more popular jpg, gif, and png formats. MrSid is especially designed for orthophotos. Because each MrSid photo covers a fairly large area I don’t need to keep track of as many photos. In order to use MrSid images in Arcview 3.2 you need to enable the MrSid Extension.
The biggest problem with these orthophotos is that they don’t have solid dates associated with them. The best dates I could come up with was that these photos were taken sometime in the early 1990s. This highlights the other problem – these photos are about 15 years old and the landscape may have changed a lot in the intervening years. I suggest checking fields against Google Earth’s photos to see what’s new.
Previous post in this series: MLI Administrative Boundaries
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