Survey and Mapping

The survey and mapping section supports Mobile District, South Atlantic Division, USACE, DOD and other federal agencies through the administration of IDIQ survey contracts. Survey services include cadastral, boundary, topographic, hydrographic, laser scanning, photogrammetric, GIS mapping and airborne topographic and bathymetric lidar.

Types of Survey Services

Cadastral

Cadastral surveys are used to document land ownership, by the production of documents, diagrams, sketches, plans (plats in USA), charts, and maps. They were originally used to ensure reliable facts for land valuation and taxation. Cadastral survey information is often a base element in Geographic/Land Information systems used to assess and manage land and built infrastructure. Such systems are also employed on a variety of other tasks, for example, to track long-term changes over time for geological or ecological studies, where land tenure is a significant part of the senario.

Boundary

Boundary surveys are the actual physical extent of property ownership, typically witnessed by monuments or markers, such as (typically iron rods, pipes or concrete monuments in the ground, but also tacks or blazes in trees, piled stone corners or other types of monuments) are measured, and a map, or plat, is drawn from the data.

Topographic

Topographic surveys measure the elevation of points on a particular piece of land, and presents them as contours on a plot.

Hydrographic

Hydrographic surveys are surveys conducted with the purpose of mapping the coastline and seabed for navigation, engineering, or resource management purposes. Products of such surveys are nautical charts.

Laser Scanning

The purpose of a 3D scanner is usually to create a point cloud of geometric samples on the surface of the subject. These points can then be used to extrapolate the shape of the subject. If color information is collected at each point, then the colors on the surface of the subject can also be determined.

Photogrammetric

Photogrammetry is the first remote sensing technology ever developed, in which geometric properties about objects are determined from photographic images. the three-dimensional coordinates of points on an object are determined by measurements made in two or more photographic images taken from different positions. Common points are identified on each image. A line of sight (or ray) can be constructed from the camera location to the point on the object. It is the intersection of these rays that determines the three-dimensional location of the point.

GIS Mapping

The most common method of GIS data creation is digitization, where a hard copy map or survey plan is transferred into a digital medium through the use of a computer-aided design (CAD) program, and geo-referencing capabilities. With the wide availability of ortho-rectified imagery (both from satellite and aerial sources), heads-up digitizing is becoming the main avenue through which geographic data is extracted. Heads-up digitizing involves the tracing of geographic data directly on top of the aerial imagery instead of through the traditional method of tracing the geographic form on a separate digitizing tablet. Survey data can be directly entered into a GIS from digital data collection systems on survey instruments using a technique called Coordinate Geometry (COGO). Positions from a Global Positioning System (GPS), another survey tool, can also be directly entered into a GIS.

Airborne Topographic

Aerial surveying is a geomatics method of collecting information by utilising aerial photography or from remote sensing imagery using other bands of the electromagnetic spectrum, such as infrared, gamma, or ultraviolet.

Bathymetric Lidar

Bathymetric surveys are carried out to map the seabed profile.