AERIAL MAPPING PROJECT APPROACH

PROJECT SCHEDULING
RODS Aerial Mapping, LLC used a variety of methods to ensure projects are completed on time. Close coordination with all sub-contractors is maintained at all times throughout projects. Project Management software allows us to plan and adjust projects as necessary to make sure they stay on a strict schedule. We are also able to use trusted sub-contractors as necessary to meet the project timeline.

AERIAL TARGETING AND SURVEY
The key to a successfully completed GIS/Photogrametric Control Project is thorough planning and reconnaissance. Prepare aerial photography flight diagrams and review ground control panel placement for conformance to TxDOT specifications. Based on the photogrammetrists need for control, the site selection for newly-monument stations will be performed in accordance with visibility for GPS measurements; Monument construction and field-referenced sketches are prepared along with aerial target construction. Recovery of existing horizontal and vertical control stations or establish ground control is performed in accordance with visibility for GPS measurements and network design. A layout of the target placement is sent to the client and approved before panels are placed.

FLIGHT ACQUISITION
Once targets have been placed in the field, RAMS will utilize our sub-contractor, Aeriel Viewpoint and one of its three twin-engine planes and a Leica RC30 calibrated camera system for photo acquisition. Photography project area at a scale and altitude that was determined by the scope of the project. Color aerial film black and white shall be used for the project. All film utilized for the contract shall be from the same manufacturer and the same lot or batch to ensure minumal variation in chemical composition. All exposures for each film strip shall be numbered consecutively starting with exposure no.1 and increasing sequentially to the end of the flight line. Photo acquisition is controlled by an onboard GPS system. Prior to flight, all photo exposure coordinates are calculated and downloaded into the computer. The onboard system navigates the aircraft precisely on the flight lines and signals the camera at each stations. Proper flight acquisiton is very critical for a successful project.

QUALITY ASSURANCE
Upon completion of the flight acquisition, RAMS will review photography for proper aerial coverage and image quality and immediately process the aerial film. Special procedures are used in the production of film for scanning. Before anything else is done to the film, it will scanned. Once scanned, two (2) sets of prints will be produced. These prints will be checked for alignment, overlap, side lap, crab, tip, tilt and control target visibility. Control point targets will be located and annotated. Upon acceptance of the above, RAMS will scan film to be utilized for triangulation and data collection. The scans will be placed in a softcopy workstation and interior orientation will be performed. The stereo model will then be checked for parallax, image sharpness and proper density and contrast. When acceptable, film will be annotated with date, photo scale, job number, flight line, number and exposure.

SCANNING
Scanning of the images will be done from Raw Negative film before annotations or any points are made. This helps reduct the possibilities of any particles or scratches to occur. Images will be scanned on a RM-3 Wehrli Scanner at a 12-micron color or black and white and put into a .TIF format. This scan resolution will insure a good scan for data collection and orthophotography. We will prepare a color photo index of the area, which will be printed out and also a digital copy of the index will be delivered. All data shipments shall be delivered on External Hard Drive. All shipments shall include an itemized list of each file contained on the hard drive. Items to be delivered includes 0.6' pixel resolution images; 8-bit, JPEG format with world files.

DIGITAL ORTHOPHOTO
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 line and spot elevations obtained by photogrammetric collection techniques. The aerial camera also undergoes a calibration during which lens distortions are measured. Then, by conbining the camera calibration results along with precuse 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 neam that every visible feature will be corrected. A typical mapping project will accurately map the ground surface, but buildings night 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, LLC can provide digital imagery that has been mosaicked. This allows for seamless, continuous imagery at resolutions greater than can be provided by simply obtaining the photography at a higher flight altitude. A mosaic can be produced from georeferenced photography produced by RODS Aerial Mapping or from the client. The benefit of mosaicking are reduced file size 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 areial triangulation and DTM data collected shall be sufficient to support the production of digital Ortho's. The steps our firm uses in digital ortho photo production are as follows:

QUALITY CONTROL
As tiles or models are completed inspection of data for acuracy and completeness is performed. As data passes the quality control inspection, it is transferred via the network to graphic edit workstations.

Horizontal and Vertical Control
An aerial mapping ground control survey is a conbination of that reconnaissance, field data collection, analyzation, conputation and documentation necessary to provide the horizontal and vertical position of specific ground points to use in setting the scale of the aerial photographs and determining the relative position of elements visible in the photographs. Standards and specifications used for aerial mapping ground control are the same as ground control for right of way mapping and design surveys and are described TxDOT's GPS Manual, Chapter 2 of the TxDOT Survey Guide, and the TSPS Manual of Practice for categories 7 and 8, Horizontal and Vertical Control Surveys. The general layout of the panels and spacing between the panels can be found in Chapter 2, Section 4 and 5 of the TxDOT Survey Guide and must be adhered to explicitly if TxDOT is to capture enough redundand ground control data to perform checks to insure the quality and accuracy of the aerial photography for detailed design. Center panels that require coordinate and elevation locative values are generally placed along the flight centerline at and wing panels that require elevation locative values are generally planced left and right of the center panels. The proposed panel layout should be reviewed and approved by the photogrammetrists and the designated client representative before paneling work begins.

AERIAL TRIANGULATION
Aerial triangulation is typically used to expand the ground control. This reduces the need for a lot of field survey and also confirms the value of existing control. RODS Aerial Mapping, LLC proposes to utilize analytical triangulation to provide the supplemental control points necessary to set stereo models in the photogrammetric instruments. Analytical Triagulation services will be performed on KLT softcopy workstation. All airborne GPS data is imported with the ground survey control prior to air triangulation. At least square adjustments are made to all measured points to expand the survey bases prior to starting the mapping process. A complete solution is performed and approved by a licensed professional. The root mean square (RMS) error of the final block adjustment shall not exceed 1/10,000 of the flying height. Pass point locations shall be manually selected by reviewing the control photography's with a pocket stereoscope. Selected pass points shall be located and labeled on the imagery side of the contact print. For combined analytical aerial triangulation each frame shall carry no less than nine pass points with the exception of end frames which will carry a minimum of six pass points. Upon completion of all triangulation work, we will prepare a formal AT report.

STEREO DIGITIZING
One of the defining services provided by RAMS is 3-D Digital Mapping. Using photogrammetric techniques, data is collected from aerial photographs exposed with a Wild RC-30 airborne camera system. Photogrammetry is the discipline of obtaining accurate, reliable information from photography. The principle is based on the observation of images from two different perspectives. A feature is view on two adjacent, overlapping photographs creating the illusion of depth, or relief. When these overlapping images are placed in a sterioscopic viewing instrument, trained personnel called operators make corrections to the images enabling the viewing area, now called a model, to be seen as a corrected, three dimensional image. Looking down on the terrain, operators collect information from the photographs by means of an XYZ digitizer. Features such as roads, sidewalks, buildings, fences, etc. are digitized and stored in a database. Each feature contains accurate horizontal and vertical coordinates maintaining its relationship with other objects in the real world. Because measurements are possible in the Z dimension, elevation data can be collected from the model to be used in the creation of a Digital Terrain Model (DTM) or a digital Elevated Model (DEM). Our Stereo Compilation Department will use the computed horizontal and vertical control point coordinates and elevation values as the control for photogrammetric instruments, KLT Softcopy, stations to collect topographic design maps at scale of the project area. All visible planimetric and DTM features interpretable from scaled photography will be plotted. Atlas collections and edit software has many automated features such as snap-to; building squaring, TIN for contouring and creating a tin surface, and many more options. These unique features allow for both greater accuracy and efficiency at the stereo plotter. These features will be determined by your scope of work. All digital mapping will comply with national mapping standards and sign off by a Certified Photogrametrist.

DEM/DTM COLLECTION
Again RODS Aerial Mapping, LLC will use Ziess P3 and KLT ATLAS softcopy for this process. RODS utilizes Atlas on-line in the data collections process. This allows for real-time TIN and contour interpolation as the break lines and spot elevations are corrected. RODS can collect the DTM as a grid of points or as a random pattern where DTM points and break lines are needed to show the terrain of the project area.

DATA EDIT
RODS Aerial Mapping, LLC CAD editing department will perform a series of essential functions on the 1" = 100' scale data base. This will include generation of counters as a Q.C. step to check for irregular spikes or gross errors in the DTM data. We will process all DTM data to support 2-foot counters. A quality control review will be performed to assure completeness and reviewed by our Certified Photogrammetrist. Once quality control and edit has been done, the data can be translated into different formats such as ASCII for GeoPack, Microstation or ACAD format in accordance with current TxDOT ACDD production criteria handout specifications. As the data is received at the edit workstation, stereo model ties are checked and joined. Stereo models files are merged and cut into approximately land section coverage's (tiles). As tiles are generated all collected features are checked for proper layer, line type, proper tie to adjacent lines and data completeness. Contact prints are checked to ensure no features have been missed in the collection process. At this time, any attribute data such as political boundaries, street names, etc. would be added.

EDGEMATING
Each coverage will be edge matched with all adjacent sections in edit so that one seamless coverage would result from combining the individual coverages. Likewise, adjacent coverages will be checked for duplicate point data such as utility poles or small buildings occirring on both adjacent sections. Duplicate points will be eliminated from one of the converages as appropriate.

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