Frequently Asked Questions
- What options are available to view ISDP Web map services?
- Why do GeoTIFF images display incorrectly in some GIS applications?
- What are tiled TIFF images?
- Why does it take so long for file transfer to begin?
- In ArcGIS, why does my DRG show up in all black?
- In ArcGIS, why does my DEM show up in all black?
- What can I do about problems downloading files?
- Why do I have trouble accessing files?
- Why are some ISDP datasets password protected?
- How do I set the spatial reference of a file using ArcCatalog?
- What are compressed or archived files?
- How do I extract ISO image data?
What options are available to view ISDP Web map services?
This URL provides a layer file (.lyr) referencing the service. You can add the layer file to any ArcMap document. One advantage of using a layer file is that the connection information is included. You do not have to make a manual connection to the server.
This URL provides an ArcGIS Explorer map file (.nmf) referencing the service. Use this option to view your service in 3D using ArcGIS Explorer. This link is not available if services are secured using token based authentication.
This URL provides the contents of the map as KML network link (.kmz) and is suitable for use in Google Earth. The KML uses ground overlays to show a rasterized version of the map. If the map is cached in a supported coordinate system, KML Regions are used. This link is not available if services are secured using token based authentication.
This URL will provide a preview of a Map Service, Image Service, Feature Service or Feature Service Layer in ArcGIS.com map. For Feature layers this will also provide access to the Feature editing capability available in ArcGIS.com. Cached Map Services will be displayed as a basemap in ArcGIS.com unless the map is in one of the Web Mercator projections (SR 102113, 102100 or 3857). This URL will not be shown for secured services.
Some of the ISDP web map services are not cached imagery services. These services will require additional time to display completely and may require that you refresh the viewer web page to display the map.
Use mouse wheel to zoom in or out of the image.
Use upper left up arrow to zoom in.
Use upper left down arrow to zoom out.
Click and drag the image to pan the image.
The 6.0 TIFF specifications provide for breaking the TIFF image into roughly square tiles instead of horizontally-wide, but vertically-narrow strips. The standard TIFF method using strips provides adequate performance for low-resolution to medium-resolution images; however, applications can more efficiently access and process large, high-resolution images in tiled format.
ArcGIS 9.2 and ERDAS IMAGINE 9.2 support 6.0 TIFF specifications, which include the use of tiled-TIFFs. Applications which do not support the 6.0 specification cannot open tiled TIFFs.
Image tiles are defined by TileWidth and TileLength. All tiles in an image are the same size. Partial tiles are not supported. If an image's total columns and rows are not a multiple of the Tilewidth or TileLength, then boundary tiles are padded to complete the tile. TIFF readers ignore padded pixels, however, the padded pixels add to the image size and waste disk space.
For more information see Section 15: Tiled Images in the TIFF 6.0 Specification.
All files in the ISDP are archived on a robotic tape system called the Indiana University Massive Data Storage System ( MDSS ). When a file download is initiated, the robotic arm retrieves the necessary tape and loads it into a tape reader. The requested file is then read from tape and transferred to a computer hard drive before the file transfer actually begins.
This whole process takes anywhere from 1-5 minutes depending on the size of the file requested and the amount of traffic on the system (larger files take longer to access, and the system is usually busiest in the afternoon).
Once the download begins, file transfer rates will depend on how fast your network link is. For wide area connections at 100Mbits/s or better, rates should range from 1-7MB/s.In ArcGIS, why does my DRG show up in all black?
Building pyramids on a DRG may corrupt the color ramp associated with the TIFF and cause the image to be displayed without color. If this occurs, simply delete the pyramid file (extension .rrd) to view the image with an appropriate color ramp. If ArcGIS asks, select the No option to build pyramids.In ArcGIS, why does my DEM show up in all black?
If a DEM has very little change in elevation, you may see the image displayed without color. This is due to the way ArcGIS is displaying the DEM values, showing a narrow area instead of the entire value set. If this occurs, right click on the layer and select properties. Select the Symbology tab and choose the Stretched statistics. Under stretch type, it may be set to None. Change the stretch type to Standard Deviations of 2 and click apply.
- Right click the .tif file and select Properties.
- Scroll down to Spatial Reference and click Edit
- Click Select, then browse for the coordinate system under Projected Coordinate Systems > State Plane > Nad 1983.
- Select "NAD 1983 StatePlane Indiana East FIPS 1301.prj" then click Add
- Click OK to close Spatial Reference Properties, then click OK to close Raster Dataset Properties.
Compressed or archived files (*.tar, *.zip, *.tgz) may contain many separate files in one large archive. An archiving program must be used to extract or unpack the files from the archive before accessing. More from IU Knowledge Base.
Option 1: Extract all images on the ISO file by burning a CD or DVD. Use your preferred CD-writing software. Note: Be sure to open the .iso file for burning to media; do not simply add the .iso file as data to be burned. Adding the file as data will save it to the medium, but will not make the medium into a replica CD or DVD image.