Google Imagery
The North Dakota Department of Emergency Services need for high resolution imagery originated from the inception of the Statewide Seamless Base Map Project in 2009. The goals of the GIS project were to create fully aggregated continuous road centerline and addressable structure location inventories across the state with sub-meter positional accuracy. The most cost-effective means to achieve this is accomplished through the use of high resolution imagery. NDDES partnered with the NDDOT photogrammetry group to complete a statewide imagery collection project consisting of approximately .9 feet pixel resolution imagery. Image collection flights started in November 2009 and were completed in November 2013. This imagery is accessible to the public via hosted Esri imagery services available from the North Dakota GIS Hub Data Portal.
When considering the long term GIS maintenance efforts needed to sustain the road centerline and addressable structure location datasets, imagery will always be of great importance. However the means in which NDDES achieves long term GIS maintenance goals via imagery changed with the opportunity for NDDES to procure Google Imagery at the end of the 2015-2017 biennium. Capitalizing on this opportunity allowed for tremendous cost savings and afforded team members preforming the image processing tasks to better focus their time on continued GIS maintenance. The purchase coverage area was for more than 50% of the State of North Dakota comprised of imagery collected in 2016 (Coverage Map).
The license will allow North Dakota’s state agencies, counties, cities, tribes and K-12/Higher education to use the imagery in web and desktop mapping applications via streaming services. Also included is use by contractors or vendors that have a formal partnership with the immediate licensees.
Imagery web services are hosted in Google’s Cloud Platform and delivered via WMS and WMTS Open Geospatial Consortium (OGC) standards via multiple virtual Sanborn Mapping Company Servers.
NDDES long term intentions encompass continued support and funding to keep the web-based imagery services up and running for end-user consumption. The major objective is to procure additional imagery in an effort to reach an entire statewide coverage then refreshing existing imagery with future imagery collections as funding allows.
Currently, NDDES shoulders the financial funding and administrative efforts for the Google imagery services. Support from all levels of users (State, County, City, Tribal and K-12 / Higher Education) benefiting from the Google imagery services is greatly appreciated. NDDES looks forward to developing partnerships to ensure the long term feasibility of this imagery for all to use.
- Instructions on how to use WMS/WMTS Services in ArcMap
- Instructions on how to use WMS/WMTS Services in ArcPro
Coordinate System and Datum Transformations
The native coordinate system for the Google files and services is Web Mercator with a WGS 1984 datum. Many end users will work in coordinate systems with a different datum (NAD 1983 for example). It will be critical for end users that require the highest locational precision to set up their working environment through the use of the appropriate geographic transformation. More information can be found here. The geographic transformation parameter is needed to overcome the locational difference between the WGS84 and NAD83 datum’s “realization points” that are about a meter apart. Without the proper geographic transformation, reprojection algorithms will not be able to resolve the last meter of positional accuracy. In order for the imagery to be positioned as accurately as possible when there is a difference between the native projection and datums of the imagery and the client viewing application, a datum conversion must be set.
Imagery Specifications
- Imagery Resolution: 15 cm
- Positional Accuracy (CE90): 1 meter*
- Spectral Bands: Blue, Green, Red
- Processing: Orthorectified and mosaicked
- Clouds: <1%
- Bit Depth: 8 bits per pixel (scaled from 12-bit source)
- Snow and Ice: Only permanent snow or snow above timberline.
- Sun Angle: >= 30 Degrees
- Smoke / Haze: <1%
- Leaf On / Off: Mix of both.
- Format: JPEG2000
- Tiling: 4,096 by 4,096
*Stated horizontal positional accuracy of the Google imagery is expected to achieve or exceed one meter (CE90) in most areas without significant vertical relief.
Google imagery is a proprietary product licensed to the State of North Dakota. The license requires attribution on any published hard copy or digital maps, including web maps. Attribution should at a minimum read “Google” and must be legible to the average viewer. Attribution graphic files are available for download here. Additional information is available from Google:
Please complete the following Organizational Usage Agreement to access the Google Imagery Services.