Digital Orthophotography and LiDAR Data Acquisition Services

The vendor is required to provide digital orthophotography and lidar data acquisition for the 2026 through 2030 flying seasons.
- GIS hardware and software
•    County uses Esri’s ArcGIS, ArcSDE and ArcGIS server software running on windows and intel hardware. 
•    The primary operations software is ArcGIS pro, version 3.5.x accessing enterprise geodatabases residing in SQL server 2017. 
•    All data deliverables must be in a format compatible with and useable in the county’s GIS environment.
- Project requirements and procedures
•    Data collection, processing, testing, and accuracy reporting for this project shall be conducted in general compliance with ASPRS positional accuracy standards for digital geospatial data, edition 2, version 2 (2024). 
•    Final data deliverables must be continuous over the entire project area and must completely fill all tile boundaries and project area boundaries as applicable. 
•    Data gaps or voids are unacceptable.
- Project control
•    The use of airborne GPS (ABGPS), an inertial measurement unit (IMU), and ground control is required.
•    Geodetic survey’s VRS and Topcon grs1 GNSS and GPS receivers were used to obtain an accuracy of three centimeters.
•    The horizontal reference for the project will be NAD 1983 (2011), single zone state plane coordinate system, with units expressed as international feet (1 foot = 0.3048 meters). 
•    The vertical reference shall be NAVD 1988 (geoid18) with units expressed as us survey feet (1 foot = 0.3048006 meters).
- Aerial photography
1. Environmental conditions
•    It shall be the responsibility of the vendor to obtain leaf and snow free vertical aerial photography between February 1 and march 8 of each flying season. 
•    Photography shall be acquired when skies are clear, free from turbulence, wind shear, and excessive smoke or haze. 
•    The ground shall be free from standing water, and snow. 
•    Photography shall be flown only during that portion of the day when the sun is 33 degrees or more above the horizon, generally between the hours of 10:00am and 2:00 pm, eastern standard time. 
•    Cloud or cloud shadows shall not appear on more than 5 percent of the area in any one photograph nor shall photography contain objectionable shadows caused by relief or low solar altitude.
2. Flying height and ground sample distance (GSD)
•    The flying height and GSD shall be appropriate to meet or exceed the horizontal accuracy specified in positional accuracy and image resolution (p.11) and produce a final orthophoto image resolution of six inches on the ground.
•    A flying height shall be selected that avoids noticeable atmospheric degradation of image quality.
- Aircraft, camera and sensor system
•    All photography will be acquired using a tested and calibrated large format strip or frame-based aerial sensor with 4-band direct image capture capability. 
•    Respondents must specify, in detail, the brand and specifications of the camera system to be used along with a description of the aircraft, sensor mount, inertial measurement unit (IMU), airborne GPS and antenna, camera and sensor hardware, focal length, the bit depth per color channel captured by the sensor, and a manufacturer’s calibration report for the sensor system.
- Flight plan
•    Flight lines and, if applicable, individual exposure stations shall be spaced to ensure sufficient side and end overlap to provide full stereoscopic coverage of the entire project area.
•    Overlap shall be sufficient to minimize excessive building lean.
•    Frame based camera system is used, end lap shall be greater than or equal to 60 percent and side lap shall be greater than or equal to 35 percent.
•    While collecting imagery, crab of the sensor shall not exceed three degrees measured with respect to both lines of flight.
•    If a “push broom” type sensor is used, the maximum speed over the ground shall not exceed manufacturer’s guidelines.
- Aerial lidar survey
1. Sensor requirements
•    The sensor must be designed and manufactured for aerial lidar survey work and coupled with an inertial measurement unit (IMU) and AGPS. 
•    It must be capable of detecting multiple discrete returns per pulse with a minimum of 4 plus the last return.
2. Flight plan and pulse density
•    first return data shall have a nominal pulse density (NPD) of 2 points and m2 or greater for the geometrically usable part of swaths, excluding acceptable data voids. 
•    The scan angle should not exceed a field of view (FOV) of 50 degrees (+/- 25 degrees from nadir). 
•    Swath overlap must be twenty percent or greater to insure there are no data gaps between usable portions of swaths.
3. Data voids
•    First return gaps in the point cloud, within a single swath, and greater than 8 square meters 2 are not acceptable unless caused by bodies of water, areas of low near infrared reflectivity, or unless the gaps are appropriately covered by adjacent swaths.

- Contract Period/Term: 1 year
- Questions/Inquires Deadline: November 5, 2025