Mercer County, Ohio | Tetra Tech R&D

Mercer County Orthoimagery and Oblique Imagery — Mercer County

Tech Tetra Tech was contracted by Mercer County, Ohio to provide orthoimagery and oblique imagery to the county auditor. Mercer County is located in western Ohio and has a population of about 40,000 and an area of about 470 square miles. Tetra Tech acquired 4-band vertical imagery and color oblique imagery. The vertical imagery was collected with an Intergraph DMC01 camera. The oblique imagery was acquired with a 5 camera system by Trackair, using five 36 megapixel Nikon D800E cameras. 40 total photo-identifiable points or paneled control points were surveyed to provide accurate ground measurements.

The DMC imagery was processed with Trimble / Inpho’s software and included aerotriangulation, orthorectification and mosaicking. The orthoimagery was delivered as image tiles in geotiff format and as one single county-wide mosaic in MrSID format. True color (RGB) and color infrared (CIR) imagery were delivered as separate datasets. The ground resolution of the orthoimagery was 0.5 foot.

The oblique camera collected for each position a vertical image and 4 oblique images; forward, backward, left and right. This resulted in a total of 37,000 oblique images that were delivered to the County. To manage this amount of data, Tetra Tech developed a geodatabase based on the County’s parcel map. For each parcel it provided a link to the 4 most significant oblique images.

The orthoimagery is publicly available on the County’s GIS website.


Renee Walmsley

(925) 584-0049