Scenario Generation from Satellite Image

¿How to generate a new scenario?

Building a new scenario from a satellite image is a very satisfying job when finally overflying your own flying site in the simulator. It may seem a complex process, but a great effort has been done to make it user-friendly, and once the satellite image is obtained, the rest is easy.

A Scenario consists of a 3D grid over which the satellite image is laid.

3D grid from a scenario under construction

IF YOU DO NOT HAVE TIME TO READ

I do not like reading manuals. I think that any information that should be in a manual, it should also be available in the software as it is being required.

Therefore, if you do not have time to read, do this:

Ge the image and the coordinates as described in the following paragraph and then go directly to build the scenario. All you need to know will also be there.

Prepare the Satellite Image

When preparing the satellite image file you must consider the following recommendations and requirements:

Size

The image can be any size in pixels. It can be rectangular.

Recommendations:
- The recommended size is about 8000 x 8000 pixels for an area of 15 x 15 km.
- It is recommended that the image represents at least 5 x 5 km.

File Format The image file format must be JPG
Coordinates

The image must be oriented with the North up, in case real coordinates are to be used.

Choose two points in the image and write down the coordinates (latitude and longitude)

The points should coincide with a tree or a house for instance, or any other object that can be easily located on the image.

The points should be as far away from each other as possible to improve the accuracy of the calculations.

Terrain Elevation Download the Elevation Data files suggested in Step 4.

Recommendations to capture the image from Google Earth

Once the are of interest is located, set the view to the North, disable the elevation and tilt down to obtain a flat and vertical view of the terrain.

The image can be saved from the File menu, save image, and selecting the largest image size, in jpg format.

With Google Earth Pro, 4800 x 4800 images can be captured, however with the standard version, the sizes of the captures are smaller. Since the recommended size is larger than one single capture, it is recommended to capture several images and stitch them together with photoshop or any other image editor. In this case, all images should be captured from the same height to make sure they can be joined.

Steps to create a Scenario

Once the image is ready, enter the Scenario Generation Tool from Main Men / Design / Scenario Generator

Follow this process to generate a new scenario from a satellite image:

  1. Select the image
  2. Georeference the image
  3. Choose the Model Initial Position
  4. Paint the Terrain Elevation Map

Press the red cross at the bottom left of the screen to exit the tool. Any progress you may have made will be stored and recalled when the same image is selected.

Step 1: Select the Image

Step 1: Select the Image file

Select the image file

Push "Select Image" button to open a dialog where you can select the jpg file of the terrain you prepared.

Name for the new scenario

Write a name for the new scenario

Sun position

This value is the position in degrees where the Sun will appear. 0 for North, 90 for East.

Select a georeferencing method

The scenario generator needs to know the Scale and the Coordinates (latitude and longitude) of the image. This is called georeferencing an image. In order to supply this information, there are three options:

1. Georeference with two points (recommended)

Use this method is you know two points of known coordinates (lat, long) on the image.
For better accuracy, the points should be as far from each other as possible.

2. Georeference with one point and the image width

This method uses one point of known coordinates (lat-long) on an image with the North up, and the image width in metres.

3. I only know the image width in metres

This method does not georeference the image, since latitude and longitude coordinates are not supplied. However, a scenario of a given size can be easily generated. The image width is the distance in metres between left and right sides of the image.

For the last two options, the image width needs to be supplied. The image width is the distance in metres between the left and right sides of the image.

Step 2: Georeference the image

Place the marks over the points which coordinates you already know, and enter their latitude and longitude. The points should be chosen to be as far away from each other as possible.

The Latitude format is: First letter N or S, space, degrees, space, minutes, space, seconds with decimal point.
For example N 37 8 48.33

The Longitude format is: First letter W or E, space, degrees, space, minutes, space, seconds with decimal point.
For example W 5 47 10.43

Move the image and the points with the mouse left button.

Zoom in and out with the mouse wheel, or using the "Page Up" and "Page Down" keys.

Step 2: Georeference the image

Paso 3: Choose the Model Initial Position

Place three Model Initial Positions wherever you like on the scenario, indicating the heading for each position.

Zoom in and out with the mouse wheel, or using the "Page Up" and "Page Down" keys.

Move the image and the points with the left mouse button.

Step 3: Model initial position

Step 4: Paint the Terrain Elevation Map

The Terrain Elevation can be applied either by importing elevation data files, or by painting the elevation with the mouse.

Importing Elevation Data Files

The elevation files required for the scenario being created are listed at the left side of the screen.
- A Green file means that the file has been found in the image folder.
- A Red file means that the file has not been found in the image folder, and need to be downloaded and copied to the image folder.

The elevation files can be freely downloaded from http://dds.cr.usgs.gov/srtm/version2_1/SRTM3

Once you have copied the files to the image folder, click on the World Elevation Map button to apply the elevation data.


Button to apply real elevation data to your scenario.

Painting the elevation with the Mouse

Paint with the mouse on the top image, and watch the results in the 3D representation below.

The 3D can be rotated with the left mouse button, and zoomed with the right button.

Step 4: Import or Paint the Elevation Map

Controls on the left side

Brushes to paint the terrain elevation
- Levels terrain (keep pressed the SHIFT key to use this function)
- Rise terrain
- Lower terrain (keep pressed the CONTROL key to use this function)

Brush sizes
Use the mouse wheel to change the brush size

Brush flow
This is the speed at which the terrain rises when the elevation map is drawn

Apply Elevation button
Applies the elevation from the downloade elevation files.

Reset button
Clears the elevation map. No confirmation asked!

Controls on the right side

Transparency
Transparency between the image and the elevation map

View Scale
Exaggerates the heights on the 3D view. Useful while editing to better visualise the elevation.
Since this scale value is not taken into account when the scenario is generated, it must be set to 1 to see the final result before proceeding to the next step.

Permanent Scale
The Permanent Elevation Scale is used to generate a scenario with exaggerated heights.

Minimum Elevation
This value is the elevation of the lowest point of the scenario expressed in metres. Will affect the altitude indicated in the flight instruments.

Enhance 3D perception
Enhance the 3D perception by applying a wavy motion to the scene.

Generating the Scenario

Press the button "Generate Scenario", or enter the Expert Mode for more settings.

Ready to generate the scenario

Expert Model settings

The Expert Model allows to edit the recommended advanced settings for a total control of the scenario generation.

The changes in the settings are reflected in a drawing with colours and lines on the right side of the screen.

The colours show the reduction in size of the textures:
1/1 White
1/2 Yellow
1/4 Magenta
1/8 Red

The lines represent the elevation grid density.

Expert Mode extra settings

Warnings
When the advanced settings are modified from the recommended values, there may appear Yellow or Red messages. A Yellow message means that the value is near its limits, and a Red message prevents the generation of the scenario. Contact us if you need to override these limits.

Tile Texture Size (pixels)
The image will be sliced in small tiles of this size.

Cells per Texture
Each texture is divided in a number of square cells, and the terrain elevation is applied to each cell vertex.

Compression Factor
This parameter reduces the total size (in Megabytes) of the 3D terrain model. The quality will be reduced on the edges of the image.

Recommended values
Push this button to reset to the recommended values

Generating the Scenario

Generating the Scenario

The scenario generation can be aborted any time by pushing the button "Abort"

Once the new scenario is generated, the simulator will load it automatically.

Sharing the Scenario (Export / Import)

The easiest way is using the Export / Import functions in the Load Scenario Menu

If you wish to copy the scenario files manually, these are the files to be copied:

MyClub.ive this is the 3D model of the scenario
MyClub_ELV.tga this is the Elevation Map
MyClub_SCN.tga this is the thumbnail for the scenario selection panel.
MyClub_SCN.txt contains the definition of the scenario and contains the elements of scene. This is a text file.
MyClub_NAV.txt contains the waypoints predefined at the model initial positions
MyClub_FCL.txt contains the description of the 3D model MyClub.ive

All the files can be found in the folder C:\Documents and Settings\All Users\Program Data\AeroSIM_RC, or C:\Program Data\AeroSIM_RC (in Vista and Windows7)

Troubleshooting

If an error occurs during the generation, check that there is enough free space in the hard disk. For instance, to process a 10000 x 10000 pixels satellite image, 250MB free disk space would be required.

If you need help with the Scenario Generator, send us an email to info@aerosimrc.com