Ortho Imagery

Ortho imagery is the next step above rectified imagery. In an orthorectified image, every point in the image is as if it is being viewed from directly above. This is accomplished by creating a digital surface model of the ground and any other features to be corrected. This surface model is typically generated from break lines and spot elevations obtained by photogrammetric collection techniques. The aerial camera also undergoes a calibration during which lens distortions are measured. Then, by combining the camera calibration results along with precise ground control points, the image can be correctly draped over the surface model. This product allows for accurate horizontal measurements between visible features on the ground. However, this does not mean that every visible feature will be corrected. A typical mapping project will accurately map the ground surface, but buildings might only be digitized at the roofline. Structures such as buildings, for example, must be mapped at both the foundation and the roofline to facilitate the proper corrections. Additionally, tall structures and areas with great ground relief might create void areas in the photography. Simply put, these are areas that the camera cannot see. RODS Aerial Mapping can provide mosaics of digital imagery. This allows for seamless, continuous imagery at resolutions grater than can be provided by simply obtaining the photography at higher flight altitudes. A mosaic can be produced from georeferenced photography produced by RODS Aerial Mapping or from the client.

The benefits of mosaics are reduced file sizes due to removal of photo overlap, and homogenous imagery where images are seamlessly matched. Digital orthophoto’s will be accomplished by using KLT Project Ortho package. The positional accuracy of pass points established by aerial triangulation and DTM data collection shall be sufficient to support the production of digital Orthophoto’s. Digital orthoimages will be delivered in a ArcGIS format, GeoTIFF file format with all georeferenced world files and the MicroStation design files assocatied with that image. The imagery will have a pixel resolution of 0.25’ with a phot scale of 1”=250’ and 1’= 40’ mapping scale. A compressed MrSID image format will also be delivered on a USB hard drive. All DTM data will be submitted in a format suitable for GIS software. The steps our firm uses in digital Orthophoto production are, 1) Diapostive Production, 2 Diapostive Scanning, 3 Geometric Transformation, 4 Radiometric Transformation, 5 Internal Mosaicing & Edge Matching, 6 Formatting, and 7) Resampling. All tiles or models are completely inspected for accuracy and completeness before data is transferred via the network to graphic edit workstations. R.A.M. provides output media, which will include DVD, external hard drive, and direct transfers via email and FTP.

R.A.M. can deliver the digital imagery in many different formats. The following image formats currently supported by R.A.M. are as follows:

TIFF Georeferenced AutoCAD, ARC/Info
JPEG Georeferenced AutoCAD, ARC/Info
SID Georeferenced Mr. Sid viewer
HMR Georeferenced MicroStation J/ V8
BMP Not Georeferenced Bitmap Format

Please contact us to determine which format will be compatible with your software.

6810 Lee Road
Spring, Texas 77379
Phone: 281-257-5249
Fax: 281-946-8251
Toll Free 1.888.456.RODS
Email: Webmaster@rods.cc