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 In This Issue In the February 2011 edition of GeoView, we feature specifics on the Q4 2010 US-Wide Parcel layer release as well as announce our new relationship to provide CARTOSAT-1/2 data to our clients. We also feature articles on Impervious Surface Mapping as well as a new online tool to search and download recent US tax roll documents.  Featured Articles Specifics on the Q4 2010 US-Wide Parcel Layer Release Impervious Surface Mapping…It's Time Has Come ImageBoost Helps eMap Clients Get the Most Out of Their Imagery The Uganda Landslides: How High-Resolution Satellite Imagery Can Help Prevent Future Disasters Satellites in the News – eMap is Ready to Provide CARTOSAT-1/2 Data to Our Clients Data in Transit – Tax Roll Data on Demand IFSAR Elevation Data Sets from Intermap Technologies In Focus – Oil in Ghana Partner Updates SPOTMonitoring Observes Iran's Bushehr Nuclear Power Plant DataMap Intelligence Lets You See the Future Before Your Competitors Monthly Columns Update on DigitalGlobe's Advanced Ortho Aerial Program Word of the Month - Ground Control Points, Part I Geospatial Freebie of the Month – ECW Compressor The Beaten Path – Love is in the Air The Speculative Tasking Program Subscribe If you would like to subscribe to our monthly newsletter, please click on the Subscribe button below. 
Featured Image of the Month 
Lake Michigan, Lincoln Park, Chicago IL The Area of Interest The Big Easy New Orleans was founded on May 7, 1718 by private bankers, the French Mississippi Company. It was named for Phillipede'Orleans, the Duke of Orleans, who was the Regent of France at that time. It was ceded to the Spaniards in the 1763 Treaty of Paris; and it remained under Spanish control until 1801 when it was transferred back to the French. Early in its history, New Orleans was known for its activity as a slave trading port which brought more than 650,000 slaves through the city. By 1840, it was the third most populated city in the nation as well as one of the wealthiest.   Justin Harmon Senior Editor Read More... » The World is Flat All the classy cars showed up for the black tire event. In a bit of a mix-up, a group of cross dressers showed up for the drag race. Jabba the Hut cannibalized his brother, Pizza Hut. All the king's men had an omelet for breakfast. Contact Us Brock Adam McCarty Chief Operating Officer 720.470.7988 bmccarty@emap-int.com  Alex Diamond Managing Director 303.877.2721 adiamond@emap-int.com Katie Nelson Account Manager 303.718.7163 knelson@emap-int.com GeoView Archive Follow the links below to find each archived version of eMap International's GeoView newsletters from 2009, 2010 & 2011. 2009 | 2010 | 2011 |
Word of the Month – Ground Control Points, Part I
Simply stated, orthorectification is the process of stretching imagery over a model of the ground below – much like draping papier-mâché over a base wire frame. In this process, the GCPs are used to position the imagery in its correct location so that, for instance, a valley in the imagery is over the same valley in the DEM. The GCPs and DEM are applied to the imagery in a remote sensing software package, such as ITT ENVI or PCI Geomatics, by employing a mathematical model (such as the rational polynomial model) to stretch and compress the data over the 'wire frame' below and thus to improve its final accuracy. There are two types of GCPs that can be used in the orthorectification process: photogrammetric control; and photo-identifiable control. Photogrammetric control (PC) must be placed in the field before the satellite or aerial imagery is collected; and as such is much less common. PC is typically created by placing a wooden or plastic panel with a large target painted in a safe location within the project site. PC can also be created by painting this large target on the ground itself. The color of the target paint and the surface it is painted on should be relatively opposite in tone – for instance, a beige target on a black wooden panel, or a black target on a white pavement surface. Here is an excellent summary (see page 10) of the suggested dimensions, materials, placement, etc. of PC in relation to the desired accuracy of the final orthoimagery. Example of photogrammetric control found in Google Earth by Farmington, New Mexico. 
Photo-identifiable control (PIC) is far more commonly used in the orthorectification process as these locations are extracted from the imagery you wish to orthorectify and then are measured in the field with a GPS unit. While PIC may not always be as accurate as PC, it can be extracted from any archived imagery source hence its popularity; and in the next WOM, we will offer tips to improve the collection of PIC. Specifically, we will focus on tips for obtaining PIC from high-resolution satellite imagery – such as IKONOS, GeoEye-1, QuickBird and WorldView-1/2. Brock Adam McCarty Chief Operating Officer Map Wizard (720) 470-7988 bmccarty@emap-int.com - Back to Main - |
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