Aerial Mapping and Surveying

Today, aerial maps are used in dozens of different online mapping and driving direction services, including Mapquest, Google Earth, Google Maps, and specialized applications to show the location of various features. Nearly every online use for online mapping is based on aerial photographs or maps. Geographic Information Systems, or GIS, is a technology using sophisticated maps created with aerial imagery via satellites to provide information about the terrain and specific land features. This imagery is available in many different scales, in both color and black and white formats, to highlight a range of features depending on the specific application.  Today there are thousands of geospatial and GIS aerial maps in use.

Aerial mapping is also very important to land surveying. While most parts of the earth have been photographed at altitude to create a map, most land surveying applications require a more detailed image of the land at a larger scale, along with the collection of more precise data points. While aerial maps for general applications are most often created through the use of satellite imagery, land surveying applications are most often undertaken with the use of an airplane or helicopter.

The main benefit of aerial methods of mapping and surveying is that they are unobtrusive, and do not require setting foot on the actual terrain. This is advantageous in situations with limited access to the land or dangerous terrain, such as areas with steep slopes. It is also important to note that aerial surveys involve the creation of three-dimensional maps through precise measurements of elevation and location, in contrast to aerial photography, which generally does not contain the same level of detail or data, although three dimensional models can be created using aerial photos.

The most common aerial surveying method is LiDAR, which uses laser beams to create a three-dimensional map or image of the land.  When combined with GPS equipment, LiDAR collects information about elevation and location that can be turned into a topographical map. This date can be used in a wide variety of applications, from the creation of topographical maps to “fly through” simulations. This three-dimensional mapping system is very popular for engineers, planners, mapping technicians, GIS professionals, and surveyors. Compared to similar methods for three-dimensional information gathering, it is very accurate, relatively fast, and cost-effective.

While LiDAR and related methods represent the cutting edge of aerial surveying, the idea of aerial mapping and surveying dates back to the middle of the nineteenth century, when hot air balloons allowed surveyors to take the first aerial photographs. Aerial surveying grew in popularity after the turn of the century. The 1957 launch of Sputnik marked the beginning of the satellite imaging era.

One of the earliest forms of remote sensing used for the creation of maps was photogrammery, a technique still used to the present day. This is the ability to determine measurements by using photography. Aerial photogrammery, achieved with a camera in an airplane, involves the taking of photographs of the ground every few seconds as the plane flies in a straight line. This technique was first used with film cameras, although today digital cameras are used. By matching adjacent images, a complete picture of the area can be created. Aerial photogrammery is used for terrain mapping, while close-range photogrammery can be used for a survey of building facades or other features. By taking photos from two slightly different angles, a three-dimensional model (or Digital Elevation Model) can be created from the data collected.

Aerial surveying and mapping methods are often preferred because they allow for the collection of data from a wide area in a short period of time, particularly when compared to traditional surveying methods. The digital data collected using these methods is useful for surveyors, engineers, geologists, city planners, and many other professionals who require highly precise visual maps of an area.

Charles Lee Iner, RLS
December 2009