Isla Blanquilla VE - ISS Island Image Transformed into EVS Precision Map
Isla Blanquilla - ISS015-E-7771 Image
A few days ago Earth Observatory carried this image of Isla Blanquilla and an interesting article about this small island located NE of Caracas Venezuela. Granted, if you are a US citizen, it is probably not your first choice to visit on a leisurely vacation due to the strained relations between our two countries, but the ISS image is pristine and details are mappable compared to the partially cloud-obscured Landsat ETM+ image. DigitalGlobe has never snapped a pic of this island either. So, I made do with the ISS image and created my map over a 4-hour period.
Isla Blanquilla - ISS015-E-7771 Georectified Image (1:62,500)
In order to use any non-georectified imagery, one must georectify it. I use Global Mapper to georectify. I loaded NGA PGS shorelines of this island (Region 14). These shorelines are very close to Landsat ETM+ shorelines. I selected 4 easily definable points on both my loaded shoreline line file and on my ISS image. It took about 10-minutes, with most of the time spent watching TV. Once the image was georectified, I began the task of digitizing the island shoreline, lower beach, upper beach, bare island, hi-low vegetation, airfield and the shallow reef surrounding the island.
Isla Blanquilla - EVS Marplot Map (1:62,500)
Once the digitizing was completed, I imported the completed layers into Marplot, where I still do much of my preliminary map construction. I am just used to working with it. I defined each layer and assigned it to pre-existing EVS layers. I did a quick layout of map titles, legend, scale and north arrow. Done!
At this point, I typically post. One day when I am given the opportunity and the time, I will "fancy" up my map using ImageForge prior to posting. Until that day arrives, this is as good as it gets.
Enjoy!
Labels: EVS, Global Mapper, ImageForge, ISS Image, Marplot, Venezuela
When comparing the photo from NASA to the imagery in Google Earth, I noticed that there is a noticeable difference in the projection of the two images. Which image do you think has been properly projected? Did you try to verify the accuracy of projection against other sources before creating your image-derived map?
Posted by
Frank Taylor |
11/30/2007 10:17:00 AM
Frank,
The ISS image after georectification is projected using Geographic (Latitude/Longitude) using WGS-84 Datum.
Mr Minton
Posted by
Mr Minton |
11/30/2007 02:12:00 PM