.. _SatelliteAccess: **************** Satellite Access **************** Lab Materials ============= Download this: :download:`SatelliteAccessImagery.zip <../_static/labs/SatelliteAccess/materials/SatelliteAccessImagery.zip>` Lab Content =========== Objective --------- STK has many applications related to geospatial analysis. The purpose of this activity is to: 1. Expose students to time-based models 2. Reinforce basic remote sensing concepts 3. Allow students to consider the possibilities offered STK 4. Test the in-class use of STK The specific activities in this exercise are creating a STK scenario, adding satellites, adding sensors, incorporating imagery and computing an access. The results of this activity will be: 1. Access report for the Landsat 5 Satellite and Gainesville, GA 2. Access report for the Landsat 5 Thematic Mapper (TM) Sensor and Gainesville, GA 3. Access report for the Landsat 5 TM and a city of your choice 4. A one page summary on this activity that discusses your experience working through the activity and possible ways that STK could be applied to geospatial analysis Procedure --------- What is STK? ^^^^^^^^^^^^ STK is Satellite Tool Kit, a simulation and modeling platform produced by Analytical Graphics Incorporated [AGI]_. STK allows the analysis of satellites, sensors, aircraft and many other objects in time based user created scenarios. STK’s tool set has expanded so far beyond just satellites that the software was being rebranded as Systems Tool Kit (still STK) in a version 10 release on November 15, 2012. The Activity ^^^^^^^^^^^^ STK can be launched from the UNG Menu under the Institute for Environmental and Spatial Analysis folder. You may have to select STK from a list of programs to launch. You may get a message about an invalid license, if so restart STK and the license should connect properly. Once STK properly launches you should be presented with the New User Setup Menu. You should be able to accept the default settings but you can change the default save folder to your GIS home folder if desired. Creating a Scenario ^^^^^^^^^^^^^^^^^^^ 1) On the welcome to STK menu, select Create New Scenario. If you are not presented with this menu, select New from the File Menu or press Ctrl + N. .. figure:: /_static/labs/SatelliteAccess/STKWelcomeMenu.png :align: center :scale: 100% STK Welcome Menu In order to create a new scenario you will need to specify a name, description, and save location. You will also need to specify a time period for your analysis. 1) For this scenario select the start time as 5 Oct 2011 00:00:00.000 and the stop time at 10 Oct 2011 00:00:00.000 and press ok. STK should launch your scenario. Creating STK Objects ^^^^^^^^^^^^^^^^^^^^ An STK scenario centers on the objects in the scenario. We can add many types of objects ranging from Aircraft to Transmitters and Satellites. We will begin by adding a satellite. You should be presented the Insert STK Objects menu when your scenario launches. You can also access the menu by going to Insert on the Main Menu and Selecting New. .. figure:: /_static/labs/SatelliteAccess/InsertSTKObjectsMenu.png :align: center :scale: 75% STK Insert Objects Menu 1) On the menu, select the Satellite object by clicking on it. In the Select a Method box, choose the From Standard Object Database option. Now click insert. AGI provides a satellite database that includes most publicly known satellites. In the top left hand corner of the box it is possible to search by common name. 2) Perform a search for Landsat by typing Landsat in the search box and clicking Search. The results should be the Landsat 5 and Landsat 7 satellite. 3) Click on Landsat 5 in the list and click the Insert button on the bottom of the menu. This should add the Landsat 5 satellite to your scenario Object Browser and your 3D and 2D views. 4) Close the satellite database and insert menus. Take some time to explore the scenario at this point by clicking and panning the globe. .. figure:: /_static/labs/SatelliteAccess/SatelliteAccess_1.png :align: center :scale: 75% Controlling Time ^^^^^^^^^^^^^^^^ STK scenarios are time based. Time can be controlled by using the time control bar. The controls are similar to what you would find on a typical tape player or DVR recorder. You will also see two additional buttons in the form of blue up and down arrows. .. figure:: /_static/labs/SatelliteAccess/STKTimeControlBar.png :align: center :scale: 100% STK Time Control Bar These up and down arrows control the speed of the scenario. The speed of the scenario can range from slow than real time to real time to (much) faster than real time. 1) Experiment with playing and restarting your scenario. You should see Landsat 5 orbiting the Earth in your 3D window. Also experiment with speeding the scenario up and slowing it down. Adding a Place ^^^^^^^^^^^^^^ We can add a city to our scenario in much the same way that we added a satellite. 1) Access the Insert menu on the Main and select New to bring up the insert menu. 2) This time select place and for the method select from city database. When you click insert, you will be presented with a menu similar to the satellite database search. Search for Gainesville in the city name search box. You should be presented a list of several Gainesvilles. 3) Select the Gainesville in Georgia and press Insert to have it added to your scenario. You should see it in your Object Browser and if you examine your map views you should see Gainesville on the map. Computing an Access ^^^^^^^^^^^^^^^^^^^ So when can Gainesville see the Landsat satellite? 1) We can answer this question by computing an Access. Right click Gainesville in the Object Browser and select Access in the drop down menu. This should bring you to the Access menu. .. figure:: /_static/labs/SatelliteAccess/SatelliteAccess_3.png :align: center :scale: 100% 2) On the access menu, click on the Landsat 5 satellite in the object list and then click on compute. This will perform the analysis. An access is when the satellite has line of sight to the city. When the satellite, for example, is below the horizon there is no access. STK can do more than calculate the access based on the horizon. For example, we would include terrain data and analyze the impact of nearby mountains on a radar facility. 3) Once you’ve clicked compute you can review the access information. An access consists of a start time (when the city can first see the satellite) and a stop time (when the city loses line of sight). An access report for the scenario time period can be generated by click on Access in the reports section of the Access menu. 4) Pull up the Access report by clicking on the access button. Print the access report to turn in with your summary. Also be sure to take a look at your 2D map to the portions of the Landsat orbit that have access to Gainesville. Once you are done remove all Accesses on the Gainesville Access menu. Modeling a Sensor ^^^^^^^^^^^^^^^^^ We can add a sensor to our Landsat 5 satellite. 1) Open the Insert menu and select a Sensor under the Attached Objects. Select Insert Default on the Select A method window. Now press Insert. 2) On the resulting Select Object menu, click on Landsat 5 and press ok. You should now see the sensor object attached to Landsat 5 in your Object Browser. .. figure:: /_static/labs/SatelliteAccess/SatelliteAccess_4.png :align: center :scale: 100% Take a look at your 2D and 3D views and play your scenario. You should see a circular sensor footprint. The default sensor is a conical sensor. We can change the sensor settings to better model the Thematic Mapper instrument on the Landsat Satellite. Right click on the sensor in the object browser and select properties. 3) On the basic definition page of the sensor, we can select the sensor type. Change the dropdown from Simple Conic to rectangular. .. figure:: /_static/labs/SatelliteAccess/SatelliteAccess_5.png :align: center :scale: 100% The Thematic Mapper instrument is a sweeping sensor that sweeps 15 degrees cross track continuously collecting data. We can model a Landsat image footprint by setting the vertical and horizontal half angle measurements to 7.5 degrees (half of the cross track sweep). 4) Press ok on the sensor properties menu. You can also rename your sensor object. 5) Right click on the sensor in the object browser and select rename in the resulting dropdown. Change the name of the sensor object to TM or Thematic Mapper. Take a few moments to play your scenario and take note of the new footprint for the TM sensor. Keep in mind that the Thematic Mapper instrument doesn’t image the entire footprint area at once but that it instead collects one thirty meter pixel at a time in a sweeping motion. This model just shows us the footprint area of Landsat image tiles and the width of the area that is collected in each pass. Computing a Better Access ^^^^^^^^^^^^^^^^^^^^^^^^^ We can now get a better picture of when we should expect to see Gainesville in an actual Landsat image. Use what you know about computing an Access to compute the access for the TM sensor and Gainesville. 1) Right click Gainesville and select access. In the object list select the TM sensor and then compute the access. Now generate the report and print it to include with your summary. Computing a Custom Access ^^^^^^^^^^^^^^^^^^^^^^^^^ Now you should have enough practice in to add objects and compute an access. 2) Add a new city of your choice from the city database and then compute its access to the TM sensor. Did TM image your city during the scenario period? Print your report to include with your summary. Experimenting with Imagery ^^^^^^^^^^^^^^^^^^^^^^^^^^ We can also add some imagery to the STK globe view. Access the Globe Manager tool on the toolbar. This will bring up the Globe Manager in the bottom of your Object Browser. Here we can add items to the 3D view. 1) Try clicking on and off the clouds option. Add an image by clicking on the terrain and imagery button. Navigate to the folder containing the imagery (you should have extracted the imagery from the zip file) you downloaded for this lab by clicking on the Ellipsis button next to the path (this is similar to connecting to a folder in ArcGIS). Once you’ve navigated to the folder the list of images will be populated with all of the images in the folder that can be overlain on the 3D view. The type of images that can be added is more limited than what we can work with in ERDAS or ArcGIS. We can add a georeferenced .JP2 image to the globe. 2) Click on the jp2 image and click Open. Now pan the globe to Gainesville and you should see a grayscale image of Band 3 of a Landsat image. Use your access report to determine when Landsat should be passing over Gainesville. Run your scenario at real time speed or slower from that time and you should see the TM sensor footprint passing over the Gainesville image area. Now go to the Glovis website and look for the most recent Landsat 5 image. The image was collected on the 5th of October, 2011. Wrap it Up ^^^^^^^^^^ You can save your scenario, we will not be reusing it in a future activity. 1) Complete the activity by writing your summary and attach your access reports. Turn in your summary in your remote sensing lab notebook with your next lab activity. References ========== .. [AGI] “AGI - software to model, analyze and visualize space, defense and intelligence systems”, n.d. https://www.agi.com/. (accessed October 9, 2012). Metadata ======== | Title:Satellite Access | CreationDate:06/20/2013 | SoftwareUsed:ArcMap | SoftwareVersion:10.1