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What projection is used for a downloaded image and World file?
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This will be specified by the world file. Our images are usually based on a WGS84 / NAD83 projection. If you need a different projection than the one used, your software should be able to reproject.
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Can the image and data be reprojected?
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We are not able to reproject the image however your software should be able to accomplish this task.
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Do I need a World file if I am just interested in looking at the image?
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Absolutely not. The World file is only necessary for users who are looking to import the image into GIS or CAD software.
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How do I download the World file?
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When you go to the page to download your digital image that you have purchased, instructions will be provided on downloading the World file.
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How do I import the image and World file into my software?
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Because every software is different, please consult your software’s help section for instructions on importing the world file and the image.
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What is GIS software?
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GIS stands for Geographic Information System, and it is a system for managing and utilizing data that is spatially referenced to the Earth. All of our images come with the necessary information to be imported into GIS software. For more information, consult Wikipedia.org.
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What is CAD software?
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CAD stands for Computer-Aided Design and it is a system that allows engineers, designers, architects, and other professionals to model a product or system on the computer and test it within a simulated environment. For more information, consult Wikipedia.org.
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What is a World file?
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A world file is a plain text computer data file used by GIS software to coordinate raster map images. The world file allows you align the image within a software.
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What all is contained in a World file?
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The world file contains six text lines that contain decimal numbers. Each line means the following:
Line 1: A, pixel size in the x-direction in map units/pixel
Line 2: D: rotation about y-axis
Line 3: B: rotation about x-axis
Line 4: E: pixel size in the y-direction in map units, almost always negative
Line 5: C: x-coordinate of the center of the upper left pixel
Line 6: F: y-coordinate of the center of the upper left pixel
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What are overlays?
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Overlays are a transparent image placed overtop of the satellite or aerial image in order to provide the user with some sort of information about the area contained within the image. This can include local roads, schools, and even areas that have experienced earth quakes within the last hundred years.
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Who can use overlays?
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Subscribers have access to the imagery overlays option. To learn more about the benefits of becoming a subscriber, click here.
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What is the data source for your overlays?
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Data for our overlays comes from various government sources. Flood data and other natural disaster data comes from the Federal Emergency Management Administration (FEMA).
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Do you guarantee the accuracy of the overlays?
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While the data in the overlays is relatively reliable, we do not guarantee its accuracy. They are a good starting point but they will not replace research when precision and accuracy are important.
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What are mapping tools?
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Mapping tools allow you to connect points and shade areas in order to better define the space in an image.
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Who has access to mapping tools?
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Mapping tools are still currently under development for the new site.
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Will mapping tools replace my need for GIS software?
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These tools will not completely replace the need for GIS software at the professional level. We do intend to provide many of the GIS features for our more casual users though.
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Do you guarantee the accuracy of your mapping tools?
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As with the overlays, these tools were not designed to replace any software. They are simply an added feature to gain a better understanding and usage of the imagery and information provided on the site. We cannot and do not guarantee that our mapping tools are absolutely accurate.
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