EarthSLOT

Help

This page mainly contains Help for EarthSLOT created Earth Models and use of TerraExplorer.

Click here for Help with Google Earth.

Click here for Help with World Wind.

Please select one of the links below for more information on EarthSLOT, or scroll down on your own:

TerraExplorer requires use of Windows XP, 2000, NT, or 98 -- it currently does not run on Mac or Unix, but this is a possibility if demand is high. Also recommend are: a reasonably fast and new CPU with at least 256 MB of RAM; free disk space of 300MB for a local cache to improve performance; and an internet connection of typical DSL or cable modem speeds (greater than 200 kilobits per second). It will run on slower connections, but may be frustrating; a connection speed of 500 kbs or higher will likely lead to an awesome experience.

- Get the fastest internet connection that you can

- TerraExplorer will cache data on your hard disk, such that if you stay in one area, you will no longer require an internet connection. The larger your cache, the more local data you will use and better your performance. Go to Tools->Options to make your cache as large as possible.

- If you have a slower connection, use this time to practice flying or turning layers on and off. Just because the imagery is still downloading doesn't mean you can't still have fun. Check your current connection speed at the lower right of the screen.

- If you have a slower connection, the MPT terrainbases will download more quickly than the TBP terrainbases.

- If you are interested in seeing the highest resolution data fast for a particular area, zoom all the way into that area and it will prioritize that area for download.

- Displaying lots of labels will make the make the flight controls feel sluggish. For best flight performance, turn off all labels and objects using the Information Tree.

- If you find that TerraExplorer is no longer downloading data, it probably means that we needed to restart the server. In this case, you will need to completely exit TerraExplorer and restart the application.

- Use the Shift key to accelerate flight motion when using the keyboard

- Click on the Globe Map in the lower left container (when available) to instantly jump to a new location.

- Don't forget that many window containers in TerraExplorer have tabs that open new windows within those containers

TerraExplorer comes with a very nice help file. After downloading and installing the program from the "Fly Now!" page, simply click on Help in the main menu.

Skyline Software also has a rich set of useful information about their products, including another their own FAQ and User Forum.

Q. When I try to launch a FLY file, nothing happens or I get an error. Why?
One reason may be that TerraExplorer is not installed properly, which can be done from the Fly Now! page; you can also download it directly from Skyline Software. Another reason may be that either the UAF network or the EarthSLOT server may be temporarily off-line. You can check real-time system status using the menu on the upper-right of the page. Lately we've noticed that the UAF Domain Name Server goes down intermittently (which we have no control over) and everything looks like it should be working except your computer cannot locate ours; try again in a few minutes in this case. Click 'more' there or here to get more information. Remember too that it only runs on a PC, not Macintosh or Unix at this time. Netscape does not correctly associate the .fly extension with TerraExplorer and so will try to load it within the browser, creating gook; Internet Explorer is the only browser that we test, and we have had no problems thus far with it.

Q. Why are things so screwy?
A. This application is still in a beta stage, so you should expect some surprises. Pages and files may come and go or change at any time. The underlying topographic and imagery information will also be updated continuously at this stage, and new FLY files will be added regularly; see the "News" section in the right-hand menu on our web pages to learn what's new. Our goal is to have global Landsat at about 15 m as base imagery, with higher resolution imagery where available; MODIS will likely fill in the gaps, as it does now. We plan to incorporate the USGS DEMs in Alaska (roughly 45 m) and most of the states. Elsewhere, we are stuck with GTOPO30, which is largely what is present all over our terrainbases now.

Q. Why does the earth look so blurry?
A. It is likely for one of two reasons. First is that we may not have higher resolution imagery available for this location. Second is that you may have a slow internet connection. EarthSLOT makes use of powerful algorithms that allow you continue to navigate around the terrain while the higher resolution imagery layers are still loading. These algorithms employ a form of image compression that only serves you as much resolution as you need for your current view, but this can still take some time using a dial-up modem. At the lower right of your screen, you will see a bar labelled "Buffering" -- the more bars you see, the closer the imagery download is to being finished. For best results, use a connection that can support 200 kbs or higher, like cable modem or DSL.

Q. Why does terrain appear to jump or move when flying?
This is probably due to your connection speed. Although the algorithms used to serve the data over the internet are quite powerful, it does take some time for the data to arrive and refresh the screen, and each additional user does place an additional load on the server. So if you approach the ground surface before higher resolution topography has been downloaded, you will likely see some funky surfaces. Be patient, it's worth the wait. Once the terrain and imagery is cached on your computer, you should no longer notice such effects in that area.

Q. Why does the imagery change across linear boundaries?
EarthSLOT can ingest imagery at any resolution. That is, we do not have to wait until we have global 5 m spatial resolution to just make use of one patch of 5 m data, we can mix and match resolutions. Therefore, it is unavoidable to have either a resolution jump or a color jump when going from one imagery source to another. The Landsat 7 mosaic we are using for the base imagery in EarthSLOT was colorbalanced to minizmize these jumps in color, but you can still see some individual tiles if you look closely (for example, visit the northeast corner of Alaska). So these linear boundaries define source data extents.

Q. Where are the flight controls?
You can use the keyboard or the mouse for navigation. Go to Help in the main menu of TerraExplorer then Flight Controls to keep them handy while flying. This is what you will find there:

Q. Why does TerraExplorer stop downloading high resolution data sometimes?
Every time we stop the server to add new data or fix something, the connection between your machine and the server ends permanently. In this case, you will still be able to fly around over the data that you already have cached on your hard disk, giving the appearance that you are still connected when you really are not. You must stop TerraExplorer and re-open the FLY file to establish a new connection. We post real-time server status on our EarthSLOT web pages in the right-hand menu bar; be sure to refresh your browser window. Often, however, our server restarts take only a few seconds, so chances are it will be back on-line before you realize it was ever off-line.

Q. How do I make movies?
You need to purchase the Pro version of TerraExplorer to do that. Contact Skyline Software for a free demo.

Q. What is a FLY file?
A FLY file is created by TerraExplorer Pro (not the free viewer called TerraExplorer) and contains all of the data you see except for the imagery and elevation. This includes the floating labels, cars/airplanes/boats, vector layers like polygons or lines, 2D objects like billboards, 3D objects like spheres/cones/cubes, as well as routes and location viewpoints. The FLY file is what makes the EarthSLOT experience rich in scientific content, as opposed to just a cool 3D visualization experience.

Q. What is an MPT or TBP file?
These files contain the terrainbase knowledge, specifically the digital elevation models that define the shape of the earth and the imagery that defines its color. An MPT file is a stand-alone file that can be transferred from computer to computer (via DVD, for example) such that it can run locally on your hard disk. In this case, all of the calculations necessary to merge the topography with the imagery have been completed. For a large area, say the state of Alaska, it can take several days of computation using multiple CPU to create a TBP file, and no new imagery or elevation data can be added to this file. So for big projects like EarthSLOT, we make use of the TBP file. Here, little preprocessing is done and most of it happens on the fly. In this way, we can add new imagery or elevation data in minutes instead of weeks. We utilize multiple CPU to keep computations happening faster than the available bandwidth, so there is no computational bottleneck, at least up to 25,000kbs which is the fastest connection we have.

Q. What is the difference between TerraExplorer and EarthSLOT?
EarthSLOT is an academic research project led by Dr. Matt Nolan at the University of Alaska Fairbanks. It makes use of commercial software components created by Skyline Software called TerraExplorer, TerraExplorer Pro, TerraBuilder, and TerraGate. Thus anyone could purchase this software and create an application similar to EarthSLOT, and EarthSLOT has no commercial connections to Skyline, though we do have a close working relationship. Our impression is that the Skyline management team has a sincere interest in education. They certainly have been very helpful to us in getting EarthSLOT funded and off-the-ground, so to speak, going well beyond a simple commercial motivation.