PlanetGIS User Guide/Getting started
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Opening a GIS project
The first time you run PlanetGIS you will be presented with the following screen:
(the Create a new map option will not be visible if you are running PlanetGIS Explorer)
The next time you run PlanetGIS you will see all previously opened maps in a growing list below Browse...
PlanetGIS projects are stored in files with .map extensions. These files store the structure of the project, all settings like styles and database linkages and references to other projects. No spatial data is stored in a .map file, instead spatial data is stored in .ent, .att and .idx files. These files do not have to be present, however you will have no features on your map. If a .map file is opened while the spatial data files are not present, those files will be created anew and will have a size of approximately 17KB.
 | Note: | It is a common mistake to omit to copy the spatial data files when moving maps around or extracting them from archives. An empty map and newly created .ent, .att and .idx with file sizes of 17KB will indicate this. |
There is an exception to this: PlanetGIS maps can be compressed to greatly reduce the size for purposes of electronic transmission. When compressing a map, an additional .fc2 or .fcz file is created. Maps may be redistributed with the .map file along with the .fcz / .fc2 file, instead of the .ent, .att and .idx files. When a .map file is opened and the usual spatial data files are not present, Planet will look for a .fcz / .fc2 file in the same directory as the .map file (and with the same name) and recreate the full map from the compressed information.
 | Tip: | Modern versions of Windows hide file extensions of "known file types" by default, which could make it difficult to work with multiple files with the same name but different extensions. To change this click Tools->Folder options in Windows Explorer and under the View tab, uncheck Hide extensions for known file types. |
Working with Multiple Projects
A PlanetGIS project might be utilizing multiple "external" projects to render a particular view of a map. Many of the sample maps on the PlanetGIS website [1] are structured in such a way. When a map1 is set up to use external maps it is best to have all the maps reside in the same directory (folder) or in subdirectories of the main or "master" map.
When moving maps around or making copies on CD / DVD / USB drives, always ensure that all external maps are copied also. When PlanetGIS can't find an external map it will prompt you to locate the map. You can at that point select Cancel after which the layers from that map will not be available.
To add layers from different maps to your current project follow the following steps:
- Open the required maps and identify the names of the feature classes you want to add to your project.
- Activate your "master" map with the Window menu.
- Activate the Displays tab.
- Click inside the Displays tab to select one or more feature classes.
You have now created a dependency between the two maps and the second map will be loaded automatically whenever you open your main project. Deleting the display (layer) you have just added to your map will free the dependency.
Adding Spatial Information from other GIS Programs
In addition to .map files, Planet GIS can also open the following types of files:
- ArcView Shape files (.shp)
- MapInfo files (.mif)
- AutoCAD Interchange files (.dxf)
- Microstation 7 Design files (.dgn)
- ESRI E00 files (.e00)
- Autodesk MapGuide SDL (.sdl)
- UK National Transfer Format (.ntf)
- ReGIS Feature files (.fea)
- EPANET input files (.inp)
- OpenStreetMap maps (.osm)
It is more accurate to think of this action as importing a spatial data exchange file into a temporary PlanetGIS project. The contents of these exchange files are converted into PlanetGIS' own data representation in memory (and saved to temporary files on your hard drive if necessary). When opening multiple files of a format that can only contain a single layer (e.g. shape files), they will all be opened in the same temporary project. Conversely, if you open multiple files of a format that may contain many layers (e.g. DXF files), a temporary project will be created for each file. (Use the Window menu to switch between projects). Some information cannot be imported into PlanetGIS' own format, for example Dimension elements in a DXF.
Most exchange file formats require a bit of user intervention before they can be imported into Planet. This is different for each type of file and explained in detail in the PlanetGIS User Guide/Reference section.
You have to save your project as a PlanetGIS project (.map) if you want to retain any further changes to it. In many cases, you would copy selected layers from your temporary project to another - already open - project for further use and manipulation.
| Tip: | If you do not copy the spatial data to a PlanetGIS project (or save it as a PlanetGIS project) and then reference it from another project (e.g. adding layers to another PlanetGIS project as described above), the original file will have to be opened (imported) every time it is required. Since opening these files usually require user interaction, this is not convenient. |
Starting from Scratch
To start a new PlanetGIS project, select Create a new map in the Quick Launch window or select the File->New menu item. (Not available in PlanetGIS Explorer). You will be asked for a location for your project.
The most common coordinate system in use today is WGS84, a geographic projection using the spherical latitude and longitude coordinates. WGS84 (World Geodetic System) defines the exact centre of mass of the earth and its major (transverse) and minor (conjugate) radius. Given spherical coordinates (latitude & longitude) and an altitude a position can be pinpointed relative to the centre of the earth. If you are dealing with maps on a global or continental scale or locations obtained from a GPS, you are most likely working in the WGS84 system. In fact, most projected systems in common use are only used over areas with an east-west extent of less than 6 degrees (UTM) or 2 degrees (Transverse Mercator), so if your data span a larger extent than that you are probably working (or should be working) in WGS84. (A notable exception to this are the conical projections used for continent and country sized extents).
For more information on coordinate systems, please see [PlanetGIS User Guide/Coordinate Systems].
You are now ready to add layers from other maps by either copying them to your new project or directly referencing them from your project. You can also capture your own information or read spatial data in from a database or GPS. (needs reference)
Viewing Raster Images in PlanetGIS
If you would like to add your satellite images or aerial photographs to a PlanetGIS map, PlanetGIS supports viewing the following types of compressed images directly:
- MrSID (.sid)
- Enhanced Compressed Wavelets (.ecw)
and will create compressed and indexed images (.ijp) from:
- Windows bitmaps (.bmp)
- JPEGs (.jpg, .jpeg)
- TIFF and GeoTIFF (.tif, .tiff)
- Portable Network Graphics (.png)
- Click Edit->Capture
- Click New->Feature class...
- Enter a name for your new feature class and select Raster image as the type
- Click Select
Next you will be presented with the Insert Image window where the first step is to click Browse... and locate your images.
| Tip: | 1. If you have multiple images, select them all at once to save you a lot of time. 2. It is recommended that you first copy your images into the same directory as the map, or a subdirectory. |
In most cases your images will have their geographic location embedded with them or in an accompanying world file. In these cases, Planet will pick the most appropriate settings for the rest of the fields, so you should be able to see all your images in their correct locations after clicking OK. (See Working with Raster Images for further information).
| Note: | Look out for world files (tiny text files with the same name as the images and similar extension altough ending with a "w", e.g. ImageName.jgw) accompanying your image files. If you are copying your images to a new location, be sure to copy them too. GeoTIFF, MrSID and ECW images do not need them. |
Interacting with Google Earth
PlanetGIS has 3 very useful ways to interact with Google Earth. (You must have Google Earth installed on your computer and some knowledge of using "GE" is assumed). The following menu commands will take you directly to GE:
- View->Current location in Google Earth
- View->Tags as placemarks in Google Earth
- File->Export...
While the first option is self-explanatory, the second option requires you to have selected one or more features on your map, of which the little yellow tags will be transferred to GE.
The 3rd option also requires one or more features to be selected. If none are selected, you will be prompted to select a whole layer. (GE was not designed to handle a vast amount of vector data in this manner). After clicking File->Export... you need to enter a name for the export file and select Google Earth KML (*.kml) or Google Earth compressed KMZ (*.kmz) in the Save as type dropdown list. Once that is done you have several options to play around with. Be sure to check Open in Google Earth so that you will be taken directly to GE with your data activated as an overlay.
For more information, see PlanetGIS User Guide/Google Earth.
Exporting Spatial Layers to other GIS Programs
For purposes of this introduction we will show you how to export spatial data to two very common file formats:
- ESRI shapefiles (.shp)
- AutoCAD DXF (.dxf)
For more information, please see PlanetGIS User Guide/Exporting Spatial Data.
When you export spatial data you can either export a selection of features on the map or export one or more entire feature classes. If you have selected features on your map the first method is automatically activated. If you want to export entire feature classes, ensure you don't have anything selected by clicking on the Clear tags button. (See the next section for an explanation of the most commonly used buttons).
Select the File->Export... menu command to export spatial information. Now you can specify the name and type of the file to be exported. Each file format has unique options for which you will be prompted.
Shape files
Shape files are the most common format of GIS data exchange. Points, lines and polygons are stored in a binary format in the .shp file as per ESRI's shapefile specification. An additional .shx file contains index entries into the .shp file to directly locate the Nth entity in the file and an optional .dbf file contains attributes in Dbase IV format. (Other files may also accompany a shape file but these are the minimum required while the .dbf file is only required if attributes are needed).
The following must be kept in mind when working with shape files:
- Shape files cannot store text. Text can only be carried as points with the text as an attribute in the .dbf.
- Shape files do not store any number that uniquely identifies each feature. This is typically carried in the accompanying .dbf file, but there is no way to know which field in the .dbf is unique and seemingly unique "ID" fields very often contain duplicates or blanks.
- Shape files are intended for one feature class only. Each feature class must be stored in a separate file.
- Shape files can only contain one type of feature, i.e. either points, lines or polygons.
When exporting to a shape file in PlanetGIS, you are allowed to select features from more than one class or select more than one entire feature class. If you provide a file name in the Export to exchange file dialog box, Planet will check that all the classes are of the same type so that they can be accommodated in the same shape file. To have each feature class exported to a different file, simply type ".shp" (without the inverted commas, note the preceding full stop). The name of each feature class will be used as the file name for each shape file.
DXF files
The most common method to import GIS information into CAD programs is through AutoCAD Drawing Interchange Format (DXF) files. This is probably the most widely used vector format, but a lot of information like keys (for linking to database information) and labels are lost.
An inportant thing to remeber is the coordinate system used with most CAD files. When exporting to DXF from Geographic Lat Lon open it again in PlanetGIS and convert to relevant Lo Y,X. To use in CAD. Remember values in Lat Lon (-25,26) is small and Y,X (2500,-2800000) is larger.
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