Optimum Viewing
The CORONA Atlas is best viewed at a resolution of 1280 x 1024 or higher. According to our testing, Mozilla Firefox, Microsoft Internet Explorer 8 & 9, and Google Chrome display the Atlas correctly. There appear to be some problems when using Internet Explorer 7, it is recommended to upgrade your browser. Internet Explorer 6 does not function properly with this website.
Basic Navigation
- Zoom In to an area by double-clicking the mouse or holding the shift key while drawing a box.
- Zoom In/Out using the mouse scroll wheel.
- Move/Pan around the map by holding the left mouse button while dragging.
- Zoom to Default view by clicking the
button in the Map Contents menu.
- Bookmarking is possible in the Atlas. Use browser capabilities for saving specific locations.
Map Layer Visibility
At the default zoom level of the atlas, basic outlines representing the footprints for available CORONA images are displayed. As users zoom in to a larger scale, the CORONA images and archaeological sites become viewable.
Map Contents Menu
Map layers can be toggled using the Map Contents menu. Some map layers are expandable, allowing sub-layers to be turned on or off. Use the plus sign(+) next to a layer to access sub-layers. Use the blue down-arrow next to an image to download the source data.
Map Layers
Map layers include populated places in the Middle East, and modern political boundaries between countries. These layers help users to navigate in the area, and can be turned off at will.
Footprints Layer
Footprints layer contains the area covered by CORONA images. At lower scales, image footprints are merged to depict separate CORONA missions for easier viewing. In higher scales, users can investigate individual footprints and turn them on and off when navigating through these images. Footprint locations and coverage are estimated via photogrammetrical methods; they are accurate representations of image areas mapped on the ground in bowtie shapes.
Sites Layer
The Sites layer includes archaeological settlements in the Atlas. This layer remains inactive at lower levels in order to provide a clearer view of the coverage. Once a certain scale has been passed, the layer can be turned on/off at the user's will. Locations and naming conventions are obtained from Oxford Encyclopedia of the Near East, Atlas of PreClassical Upper Mesopotamia (APUM) and ANE Placemarks for Google Earth of Uppsala University. By adhering to these conventions, we hope to maintain standardization in the site inventory, and overcome further confusion by adding secure ancient names of settlements, if available and when possible..
Corona Layer
The Corona map layer contains all Corona images available for viewing and download. For efficiency this layer is only active at or below a certain zoom level, and is therefore not viewable when the Atlas is initially opened.
Images within the Corona map layer are organized by satellite revolution (or pass). During the collection of Corona imagery, a number of satellites were successively launched and each launch was counted as a new Corona mission. During each mission, the imaging satellite orbited around the earth a number of times -- each orbit was considered a separate revolution. The mission number and revolution number for each image are recorded in the image name. For example, image DS1105-1009DA003 was captured during mission 1105-1 and revolution 009. The last four characters (A003) tell us it was the third aft image taken during that revolution. Image acquisition dates are also provided in parenthesis, located in the parent mission-revolution names tab.
Nearly all images obtained for this Atlas were capture by the KH-4B CORONA instrumentation. Due to the stereo camera design of the KH-4 satellites, most revolutions available within the Atlas contain both forward and aft -- nearly 100% overlapping images (during some missions, one camera failed to return usable images). Beyond this, some revolutions overlap one another resulting in multiple views for any given location. Again, the Map Contents menu can be used to turn these layers on and off as the user desires.
Beyond overlapping fore and aft images, other forms of overlap exist and are important for the user to understand. The most basic of these is overlap between consecutive images (demonstrated by the red areas in the figure below). Another form of overlap results from revolutions overlapping one another (demonstrated by the blue areas in the figure below), resulting in multiple views for certain locations.
Due to the imaging geometry of CORONA, each image has a different, but compatible photogrammetric model. These models aim to reconstruct image-ground relations in the imaging sensor and are prone to variations as some of the physical camera parameters are not available. Therefore, spatial accuracy is not standard throughout the Atlas, and two CORONA images overlapping in an area may not perfectly match. In these cases selecting an image to download can be determined by visual inspection with the tools provided in the Atlas.
Tools Menu
By default, the tools menu is collapsed. To expand and view this menu, click the small circle to the left of "Tools."
There are three tools available within this menu: transparency, swipe, snapshot, and measurements.
Transparency Slider
The transparency slider allows the user to adjust transparency for the CORONA imagery. When the slider is on the left hand side, modern satellite imagery becomes more visible. As the slider moves to the right, on the other hand, the CORONA imagery becomes visually dominant.
Swipe
The swipe tool divides the area into two viewing parts, and enables user to view underlying layer without actually turning on and off layers. In this tool, the left view is dedicated to CORONA, and the right view is for the modern imagery. The user can swipe the images horizontally by pressing and catching the divider with the left mouse button.
Snapshot
The snapshot tool generates a CORONA image stored in portable network graphics (png) format. After navigating to a desired area, the user can utilize this tool to get a copy of the CORONA image with a spatial coverage defined by a bounding-box. The coordinates of this box are reported in the URL of the Atlas. The numbers reported here come from a WGS84 Web Mercator Projection, and represent the corners of the CORONA image in the viewer.
Measurements
The measure tool allows for location, distance and area measurements. Two-dimensional measurement results appear in different selectable units next to the measure button. Resulting location measurement is reported in geographic coordinate systems in degrees, minutes, and seconds.
To measure a line:
1. Click the line measurement tool.
2. Move cursor to the starting point, and left click.
3. Drag the mouse cursor across the measured distance.
4a. Double left click the mouse button if you want to end the measurement at the second point to create a line segment. Reported distance measurement is the length of that segment.
4b. If measuring multiple line segments, once the next point is reached left click once to add another point (vertex) to mark the location. Continue until the last node, and double click to finalize the measurement. Reported distance measurement is the sum of individual line segments.
To measure an area:
1. Click the area measurement tool .
2. Move cursor to the first point of the area, and left click.
3. Delineate the area by adding more points (vertices).
4. Double left click when the polygon defines the desired area. The result is reported in the tool area.
To locate a point:
1. Click the point tool.
2. Move cursor to the interest point, and left click.
3. The location is marked with a flag and reported in the tool area.
Archaeological Sites Menu
The Archaeological Sites Menu is an alphabetical list of known archaeological sites within the Atlas' region. The user may scroll through the drop-down menu to view the list of sites. Clicking the site name in the drop-down menu zooms to the site's location on the map. The name of the site is also displayed in the viewer which can be turned on and off from the Sites layer of the Map Contents.
Saving the Snapshot and Downloading
CORONA images can be acquired from the viewer in two ways.
1. Using Snapshot functionality located in the Tools creates screen images of the CORONA, ready for viewing. After the user clicks the snapshot button, the image opens in a separate browser. Browser functionalities then can be used to save the data locally in the PNG format. The stored image is orthorectified so that shapes are preserved.
2. Downloading spatially corrected CORONA imagery in its entirety is also possible through the Atlas. For these images, the data is stored in Imagery Transmission Format (NITF). The user can start downloading data to a local directory by clicking the arrow button located to the right of the CORONA image ID.
Using CORONA Images in Other Platforms
As an emerging standard, each National Imagery Transmission Format (NITF) file available for download contains one unprocessed CORONA image, along with a replacement sensor model (in the form of Rational Polynomial Coefficients - RPC) used to map the image to the ground. RPC information generated from inhouse control point measurements and software. Once fully downloaded, these images can be viewed in many Geographic Information Systems (GIS) software and remote sensing platforms. These images are not orthorectified, however, and require further processing. To help facilitate this process, we have prepared, and made available for download, SRTM DEM files for each Corona revolution
HERE. Information on using ArcGIS to orthorectify the NITF files using the provided elevation data can be found
HERE.
As one of the main advantages of NITF, with some additional processing users can geometrically refine images if they provide additional ground control points number in various off-the-shelf photogrammetric software.
SRTM Credit:
Jarvis A., H.I. Reuter, A. Nelson, E. Guevara, 2008, Hole-filled seamless SRTM data V4, International Centre for Tropical Agriculture (CIAT), available from
http://srtm.csi.cgiar.org (last accessed November 01, 2011)
Archaeological Inventory Credits:
S. Anastasio, M. Lebeau, and M.Sauvage (eds.) 2004. Atlas of PreClassical Upper Mesopotamia (APUM), Brepols Publishers.
Eric M. Meyers (ed.) 1996. The Oxford Encyclopedia of Archaeology in the Near East, Oxford University Press.
Olof Pedersen. ANE Placemarks for Google Earth, Uppsala University http://www.lingfil.uu.se/staff/olof_pedersen/Google_Earth/ (last accessed November 01, 2011)
