Importing Your Data Into Google Earth
Use the Data Import feature to import your custom geographic data into Google Earth and view it as you would any of the layers in the Layers panel. When you use this import feature, you are importing two basic kinds of data:
- Vector Data - Vector data consists of points, lines, paths, and polygons. Typically, point data is used to describe specific locations, such as the center of a city. Lines and paths can be used for road or boundary data, for example, while polygons might be used to describe parcel data or define other areas such as lakes.
You can import vector data into Google Earth from third-party data providers, such as ESRI. In addition, you can use generic text files to import point data that you define yourself.
Once you import vector data into the Google Earth application, you can change its appearance or content in the same way you would when editing placemarks and folders. In addition, you can use Style Templates to format your data in visually meaningful ways. You can also display KML data in a time sequence. To learn more, see Viewing a Timeline.
- Imagery Data - You can import imagery data such as aerial maps or topographical maps and have the imagery properly projected over the base imagery in the 3D viewer. For this to work, the imagery file itself must be in the proper format. Imagery of this type is referred to as GIS imagery.
Note - The GIS import feature is available only to Google Earth EC and Google Earth Pro users. However, all versions of Google Earth can import generic text files.
Once you import vector or imagery data into the Google Earth application, you can save your modified data just as you would other types of placemarks or overlays.
Importing Vector Data
Google Earth supports the following kinds of vector data:
- Lines and paths
- Polygons, including filled polygons
The process of importing vector data files is simple:
- Import the vector file using one of the following ways:
- Drag and drop - Locate the file on your computer or a network server and drag it over the Google Earth 3D viewer.
- Select Open or Import... from the File menu - When you choose this option, you can specifically select the type of data you're importing (i.e., TXT, SHP, TAB) or indicate All data import formats from the select menu.
You can also open a file from a machine on the network as you would open any file. In addition, if you want to open a file located on a web browser, you must first download the file and all related files to your computer or local network and then open it.
- At the prompt, choose whether or not to apply a style template. If you select Yes to apply a style template, you can define a new one at that point, or select an existing one if one has already been defined for that data file. For more information, see Using Style Templates.
Once imported, the vector elements appear in the 3D viewer and the imported file is listed under the Temporary Places folder. Labels, icons, color, and description appear just as they do for other types of places and folders depending upon how you have defined them using the style template.
Note: If you don't use a style template to modify the appearance of the data you've ingested, Google Earth looks for a Name field to use as the label for your data. This label appears in the 3D viewer next to points as well as in the listing beneath Temporary Places. If your data does not contain a Name field, the first available field that contains text is used as the label for data.
The rest of this section covers the following topics:
Using Third Party Vector Data
Google Earth EC and Google Earth PRO users with the data import module can import the following vector file formats:
- MapInfo (TAB) - Required files include:
- ESRI Shape (SHP) - Requires SHX
Projection information, which can either be built into the SHP file or defined in a separate file with a PRJ extension
DBF (for viewing field data)
Most third-party GIS vector data comes as a collection of related files that operate together to produce all the vector data you see in Google Earth. Be aware that if expected data does not display in the 3D viewer, it might be due to missing support files. Those vector file types that require additional support files are indicated in the list above.
Note - You can also use generic text files to create your own point data for use in Google Earth. This feature is also available to Google Earth Plus users.
Using Generic Text Files
In addition to importing vector data in SHP, TAB, and other formats, you can define your own point data and import it into Google Earth.
Note - Only point data can be created and imported using generic text files.
Generic text files need named columns whose values are separated either by commas, spaces, or tabs. Do this by creating your data in a spreadsheet application such as Microsoft Excel and then saving the file as either CSV or TXT format. Alternatively, you could use a programmatic method to extract data from a database and produce a final output file in either CSV or TXT format.
Note - If you attempt to import more than 5000 features (i.e., 5000 point data lines) into Google Earth, this process can take a long time.
For more information on using generic text files, see:
Required Location Fields
At minimum, generic text file that you import must contain one or more fields that specify the location of the point on the earth in order for the data to be correctly positioned in the 3D viewer. This can be specified either with address fields or with geographic coordinates.
Note - You cannot use a mix of geographic coordinates and address fields in a single file.
Your data file can use street-level addressing to position each point on the Earth's surface. Google Earth can ingest georeferenced and non-georeferenced information. At this time, Google Earth can only ingest such information for addresses located within the United States, United Kingdom, Canada, France, Italy, Germany, and Spain. Google Earth cannot place any address that contains a P.O. box.
The following types of address formatting are supported:
- Single-address field - You can define the street, city, state, country, and zip code in a single field. For example, a single field with the column label of address might have the following value:
123 Easy Street, San Jose, CA, 95330
Multiple address fields - You can also define street, city, state, country, and zip code in multiple fields. In this case, a field with a column label of street would have as its value:
123 Easy Street
In this scenario, additional fields would be defined for city, state, and zip code.
- Partial address default values - Because some of your points might have only partial addresses, you can use the data import wizard to define default values for missing fields, such as state or zip Code.
Using Geographic Coordinates
You can use geographic coordinates (latitude, longitude) to indicate the position of the point data in your text file. For importing generic text files, Google Earth supports coordinates described in
- Degrees, minutes, seconds (DMS)
- Decimal degrees (DDD)
- Degrees, minutes, with decimal seconds (DMM)
Refer to Entering Advanced Coordinates for a detailed description of the latitude/longitude coordinates supported in Google Earth as well as the type of syntax supported.
Optional and Descriptive Fields
You can use any number of fields in your custom data file to label and describe the points and display them the Google Earth application. Optional fields can be defined as the following values:
- Text or strings - A string field can contain both numbers and alphabetic characters. What actually defines a string with respect to style templates is that the string itself is either enclosed in quotation marks, or contains white space so that it cannot be interpreted as a number.
This is an important distinction to keep in mind when using style templates applied to fields.
- Floating point value
With style templates, you can take advantage of these field types to create useful visual effects in the 3D viewer such as graphs or color-coding of data based on the values in the fields.
Viewing Vector Data Fields
After you have imported vector data into Google Earth, you can use the Table Window to display the data fields contained within the vector data. To do this, select Table from the Tools menu. The window appears over the Google Earth application, listing the data fields of all placemark items in tabular form.
The Table window displays internal data fields for all vector data currently listed as well as all other entries in the Places panel. You can use the scroll bar to the right of the window to scroll through numerous entries, and you can collapse the display of items you don't want to see by removing the check next to the name of the item you want to minimize.
The Table window offers the following features:
- Sort the data by selected columns by clicking on the column header for the field you want to sort by. With this feature, you can easily view all elements in the data list and view these elements in the 3D viewer.
- Single-click an item in the table to highlight that item in the listing under the Places tab.
- Double-click an item in the table to fly to it in the 3D viewer.
- Right-click (CTRL click on the Mac) any table row to access the following pop-up menu, which you can use to sort or modify the field display.
Modifying Vector Data Display
When you import point and line vector data into Google Earth, you can determine how you want your data displayed in one of two ways:
- Apply a unified display across all data - Do this either by applying shared styles across a given folder, or by applying a style template to your vector data. For shared styles, follow the guidelines in Editing Places and Folders for details on setting shared altitude, line, label, and icon properties. Style templates can be applied to your imported data at any point in time.
- Edit individual data elements or folders - Follow the guidelines described in Editing Places and Folders for information on editing individual placemarks.
You can open GIS imagery files in Google Earth and have the files correctly projected over the proper map coordinates in the 3D viewer. Google Earth supports the following types of GIS imagery:
- TIFF (.tif), including GeoTiff and compressed TIFF files
- National Imagery Transmission Format (.ntf)
- Erdas Imagine Images (.img)
In addition, you can also import the following images. Because they do not contain projection information, you must manually edit their coordinates for correct positioning:
- Atlantis MFF Raster (.hdr)
- PCIDSK Database File (.pix)
- Portable Pixmap Format (.pnm)
- Device Independent Bitmap (.bmp)
Note - All imagery files must contain the correct projection information in order to be accurately re-projected by the Google Earth software.
The rest of this section covers:
Opening GIS Imagery
Use any one of the methods below to open the imagery file in Google Earth:
- Select Open from the File menu.
- Drag the desired file from an explorer window and drop it over the viewer.
Google Earth then attempts to reproject the image to a Simple Cylindrical, WGS84 coordinate system. From this, it creates an overlay with the image converted to PNG format. The overlay edit window appears, and you can set the location of the new overlay in any folder inside the Places panel. You can also set the properties for the GIS imagery as you would any other overlay.
The following should be noted when importing GIS imagery data:
- The reprojected image is saved as an overlay. The image is saved under the Google Earth directory on your hard drive. The name of the PNG file is based on the source file name and the scaling or cropping parameters selected when importing the overlay. (See below for more information on scaling or cropping an image.)
- Images that exceed the maximum texture dimensions must be either cropped or scaled. A dimension of 2048x2048 pixels is typically supported by high-end graphics cards, while on laptop computers, the maximum dimension can be 1024x1024 or even less. (Very good cards can support up to 4096x4096.)
Determine the maximum allowable texture dimensions for your computer by selecting About Google Earth under the Help menu. The texture size for your computer will be listed next to the Max Texture size label.
Your image cannot exceed the dimension listed in the Max Texture label (in either direction).
If you try to import an image file that exceeds the allowable texture dimensions, a dialog box prompts you to either scale or crop the image.
When you select the crop option, the viewer flies to the location of the input image and contains the extents of the input image. You then select the center point of the inset image you want to create. The client computes a maximum area centered from the selected location.
- Scale - This option scales and reprojects the entire image at the same time so that it preserves the aspect ratio of the input image and fits the results in texture memory. The typical size for the resultant image is 2048 pixels along the longest side.
- Crop - This option preserves the original resolution of the input image while creating a subset of the original input file in order to fit it in texture memory.
- For larger image files, reprojection can take some time.
If you have cropped or scaled an input image, or if you are reprojecting an image that uses more texture memory, you will see a progress meter while the reprojection occurs. You can cancel the operation at any time. Images that contain no projection information are treated as ordinary overlay files.
In this case, you can position the image manually as you would an overlay image.
- Images that contain incorrect or unsupported projection information will not be imported.
In this case, a dialog box indicates that the reprojection cannot be performed and the image will not be imported.
Note - Currently, files using NAD83 projection are not supported by Google Earth.
Saving GIS Imagery
Once you have imported imagery data into Google Earth, you can save content changes made to the imported GIS data as follows:
- Move the imported imagery to remain in your My Places folder - If you have already placed the imagery overlay within the My Places folder, any changes you make to it are automatically saved and viewable each time you start Google Earth.
- Save the imagery overlay as a KMZ file - If you wish to remove the imported imagery from your My Places folder, you can right-click (CTRL click on the Mac) on the item and select Save As... from the pop-up menu and save the GIS overlay as a KMZ file to your computer's hard drive or other accessible file location. After that, you can delete the overlay from your My Places list and open it later when you need it.
A Note About Projections and Datums
Google Earth uses Simple Cylindrical projection with a WGS84 datum for its imagery base.
- Simple Cylindrical (Plate Carree) Projection
- Google Earth Image Base
Typically, the data you import into the Google Earth application is created with a specific geographic coordinate system, such as a Universal Transverse Mercator (UTM) projection and a NAD27 datum (North American Datum of 1927). Each geographic coordinate system may assign slightly different coordinates to the same location on the earth. When you import data into Google Earth, your data is interpreted according to the Google Earth coordinate system.
In the majority of cases, reprojection works as expected. In some situations, the transformation might not work properly. In that case, you can use a third-party tool to transform your data from its original coordinate system into the one used by Google Earth.
The rest of this section provides a brief overview of map projections and datums.
What is a Map Projection?
A map projection is a mathematical expression that is used to represent the round, 3D surface of the earth on a flat, 2D map.
- 3D Earth
- Mercator Projection
This process always results in distortion to one or more map properties, such as area, scale, shape, or direction. Because of this, hundreds of projections have been developed in order to accurately represent a particular map element or to best suit a particular type of map.
Data sources for maps come in various projections depending upon which characteristic the cartographer chooses to represent more accurately (at the expense of other characteristics). In the example above, the Mercator projection preserves the right angles of the latitude and longitudinal lines at the expense of area, which is distorted at the poles, showing the land masses there to be larger than they actually are.
The following are some common map projections:
||Albers Equal Area Conic
||Typically used for small regions or countries extending in an east-to-west direction, but not continents. Preserves angles between meridians and parallels. Attempts to minimize distortion for both shape and linear scale, but neither is truly correct. The example here shows how this projection looks over the entire earth.
||Oblique Mercator (Hotine)
||A cylindrical projection like the Mercator projections, but where the cylinder is shifted to align with a region that is oblique and follows neither a north-south nor an east-west axis. The region to be mapped typically is a small portion along the length of the meridian and close to it laterally. For example, this projection was developed originally for mapping the Malaysian peninsula.
||Used by the National Geographic Society for mapping most continents. This projection is a three-point equidistant one, intended to preserve the distance between three reference points relative to any other point.
||Lambert Conformal Conic
||A projection ideal for middle latitudes and/or where the territory to be mapped has an east-west orientation. This projection is often found in USGS maps created after 1957. Scale is most accurate at the expense of area.
When building whole-earth databases, a single global projection is the most convenient to use. Google Earth uses Simple Cylindrical projection for its imagery base. This is a simple map projection where the meridians and parallels are equidistant, straight lines, with the two sets crossing at right angles. This projection is also known as Lat/Lon WGS84.
- Simple Cylindrical (Plate Carree) Projection
- Google Earth Image Base
What Is a Datum?
While a projection is used in mapping to define the earth on a flat surface, a datum is used to describe the actual shape of the earth in mathematical terms. This is because the earth's surface is not perfectly round, but ellipsoid in shape. A datum also defines the association of latitude and longitude coordinates to points on the surface of the earth, and defines the basis for elevation measurements.
As with projections, there is more than one mathematical interpretation of the earth's shape. Google Earth uses WGS84 datum.
- North Pole
- South Pole
- Semi-minor axis or polar radius
- Semi-major axis or equatorial radius