Overview of Nearmap Imagery Service
Nearmap is a commercial aerial imagery and geospatial data service provider that delivers some of the most regularly updated and high-resolution satellite imagery currently available. These images are generated from individual aerial photos that are automatically captured by an aircraft, which makes regular or scheduled flights over very large survey areas of entire cities or regions, usually between 700 km2 to 10,000 km2. For more details, please visit the Nearmap website.
Nearmap provides frequently updated, high-resolution aerial imagery of urban and regional areas, including cities and suburbs that cover 80% of the US population, 65% of Canada’s population, 95% of Australia’s population, and 75% of New Zealand’s population. This is a credential-based service, which gives users with access to the Nearmap imagery service rights to the use of this mapping service.
For every location included under the Nearmap coverage program, the map displays the number of planned captures per year, as well as the type of content (currently Vertical, Oblique, 3D) available for that area.
Using the following table, the user can find the coverage of the Nearmap service for different regions.
|The United States and Canada
Nearmap measurement tools use local representations of the Earth’s surfaces that are typically accurate to +/- 15cm for distances up to 200m.
Nearmap’s vertical imagery is made up of mosaics of orthorectified images. This means that each raw photo of the Nearmap imagery has the full orthorectification process applied, including the removal of terrain distortions, lens distortions, etc. Individual orthoimages are then merged into a mosaic, which is the map image that is visible to the end users. Nearmap’s processing system can handle difficult situations such as cloud and smoke, and it has a far lower blunder rate than older orthophoto solutions. Their imagery processing is fully automated and is intended to generate Nearmap images everywhere in the world without the need for any ground control point data.
Nearmap’s capture procedure utilizes GPS coordinates, which are improved further using PPP (Precise Point Positioning). As a result, the generated imagery is georeferenced at the time of collection using International Terrestrial Reference System (ITRF2014).
Types of Nearmap Images
The various image types offered by Nearmap are as follows:
- Nearmap Vertical: These image types are vertical photographs taken from an infinite distance looking straight directly below an observation point, which is then used to create orthophotos. The captured images are then further geometrically corrected to utilize them as a map. In these vertical images, multiple geometric transformations are applied, depending on the perspective and terrain corrections required on a particular part of the image.
The following datum/projections are supported by NearMap vertical images:
- WGS84/Spherical Mercator
- GDA94/MGA – AU
- GDA2020/MGA – AU
- NAD83/UTM – US/CA
- Nearmap Oblique: These image types are aerial photographs taken at an angle that provides a better viewing angle and allows the user to view locations from multiple directions. Typically, oblique photographs are captured at an angle of 45-degrees, which is considered the most preferred angle. Due to its capturing angle, oblique imagery allows viewers to see and measure not only the top of objects, but the side view of the objects as well.
- Nearmap Panorama: These images types are essentially photographs with a wide format, taken vertically or horizontally. These photos are taken by capturing a series of photos which overlap to create one single image. The panorama imagery provides a 45-degree view of a location and can be viewed from each cardinal direction.
The image datum/projection supported by Nearmap panorama image is WGS84/Spherical Mercator.
Importing Nearmap Imagery Service
The Nearmap Imagery Service is added into the CivilGEO software as a base map service using the Add Base Map Layer command. A base map layer provides high-quality background aerial and other imagery from different online map providers to add context to the engineering data being displayed on the Map View.
Follow the steps below to use Nearmap Imagery Service in our software:
- Right-click on the Map Data Layers panel and then select Add Base Map Layer from the displayed context menu.
Alternatively, the user can select the Add Base Map Layer command from the Map Data ribbon menu.
- The Add Base Map Layer dialog box will be displayed.
- Select the Commercial Aerial Maps panel in the Add Base Map Layer dialog box. In this panel, the user can select the Nearmap service.
- After selecting Nearmap as the base map option, click the [OK] button and the Nearmap Authentication dialog box will be displayed.
- The user can authenticate service usage by entering the API key value. After entering the authentication details, click the [OK] button and a base map of the entire world will be displayed. In addition, the corresponding Nearmap layer will be created in the Map Data Layers panel.
- The user can now either zoom in to any location from the Map View or add a terrain surface (DEM) to the project. As you zoom and pan about, the base map will refresh to maintain the quality of the display.