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Geospatial Technology

What are GIS maps and how do we use them?
 
Maps have traditionally been made using pen and paper, but the advent and spread of computers has revolutionized cartography. Cartography or mapmaking (in Greek chartis = map and graphein = write) is the study and practice of making maps or globes. Most commercial quality maps are now made with map making software that falls into one of three main types; CAD, GIS, and specialized map illustration software.

The term geomatics is fairly young, apparently being coined by Dubuisson in 1969. It is commonly defined to include the tools & techniques used in land surveying, remote sensing, Geographic Information Systems (GIS), Global Positioning System (GPS), and related forms of earth mapping. The term geomatics has been adopted as the International Standard although some have shown a preference for the term "geospatial technology."

Geospatial Information


GIS Cartography

Geographic Information Systems
 
GIS is a system for creating and managing spatial information and associated attributes. In the strictest sense, a GIS is a system capable of storing, editing, analyzing and displaying geographic information. In a more generic sense, GIS is a "smart map" tool that allows users to create interactive queries and searches to analyze spatial information and edit data.

Geographic information can be used for scientific investigations resource management asset management development planning , cartography and route planning. For example, a GIS might allow emergency planners to easily calculate emergency response times in the event of a natural disaster , or a GIS might be used to find wetlands that need protection from pollution. GIS data represents real world objects (roads, land use, elevation) with digital data. Real world objects can be divided into two abstractions: discrete objects (a house) and continuous fields (rain fall amount or elevation). There are two broad methods used to store data in a GIS for both abstractions: Raster and Vector.

Raster Data

Raster data type consists of rows and columns of cells where in each cell is stored a single value. Most often, raster data are images (raster images), but besides just color, the value recorded for each cell may be a discrete value, such as land use, a continuous value, such as rainfall, or a null value if no data is available. While a raster cell stores a single value, it can be extended by using raster bands to represent RGB (red, green, blue) colors, color maps (a mapping between a thematic code and RGB value), or an extended attribute table with one row for each unique cell value. The resolution of the raster data set is its cell width in ground units. For example, one cell of a raster image represents one meter on the ground.

Geographic Layers

Overlaying GIS layers to make maps


VRS




Vector Data

Vector data type uses geometries such as points, lines, or polygons, also called areas (shapes bounded by lines), to represent objects. Examples include property boundaries for a housing subdivision represented as polygons and well locations represented as points. Vector features can be made to respect spatial integrity through the application of topology rules such as 'polygons must not overlap'. Vector data can also be used to represent continuously varying phenomena. Contour lines and triangulated irregular networks (TIN) are used to represent elevation or other continuously changing values. TINs record values at point locations, which are connected by lines to form an irregular mesh of triangles. The face of the triangles represent the terrain surface.


GPS Mapping

Global Positioning Systems
 
The Global Positioning System is a satellite navigation system used for determining one's precise location anywhere on Earth. The system is an intermediate circular orbit satellite constellation of 24 satellites. Many refer to the system as the NAVSTAR GPS - Navigation Signal Timing and Ranging Global Positioning System.

The more satellites used the higher the accuracy of location. The precision of the GPS signal itself is about 20 meters (65 ft). Using differential GPS and other error-correcting techniques, the precision can be improved to about 4 inches or less. If desired GPS surveys can provide sub-centimeter accuracy.
The GPS system was designed by and is controlled by the United States Department of Defense and can be used by anyone, free of charge. The GPS system is divided into three segments: space, control and user. The space segment comprises the GPS satellite constellation.

VRS Corrections The “Virtual Reference Station” (VRS) concept is based on having a network (spaced at 50-60kms) of GNSS (GPS or GPS/GLONASS) reference stations permanently connected to a control center via the Internet.

Virtual Reference Station

Network RTK Delivery Services


John Schweisinger


GPS


CAD

Computer Aided Drafting
 
Computer aided design (CAD) is the use of a wide range of computer based tools that assist engineers, architects and other professionals in their design activities. It is the main geometry authoring tool within the Product Lifecycle Management process and involves both software and sometimes special purpose hardware. Current packages range from 2D vector based drafting systems to 3D parametric surface and solid design modelers.

CAD is sometimes translated as "computer assisted", "computer aided drafting", or a similar phrase. Related acronyms are CADD "Computer Aided Design and Drafting", CAID Computer Aided Industrial Design and CAAD "Computer Aided Architectural Design". All these acronyms are essentially synonymous, but there are some subtle differences in meaning and application.

Our company will convert CAD files into GIS for use in ArcGIS and Google Earth. CAD maps may be overlaid with other GIS data and basemap layers to conduct environmental assessment and impact reports from development projects. The use of CAD files in GIS and other geospatial programs such as Google Earth has become an industry standard for viewing data. Upload your CAD files to the Turf Image Cloud and download a GIS ready file.

Conversion

CAD to GIS




Remote Sensing

Spectral Signatures
 
Remote Sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object.

The basic unit used in remote sensing is the wavelength of reflectance which is measured in nanometers (nm). This kind of data collection normally makes use of the emitted or reflected electromagnetic radiation of the examined object in a certain frequency domain (infrared, visible light, microwaves). This is possible due to the fact that the examined objects (plants, houses, water surfaces, air masses ...) reflect or emit radiation in different wavelengths and in different intensity according to their current condition. These levels emitted by different objects are commonly known as their "spectral signature".

Reflectance Patterns

Wavelength Reflectance




Vegetation Mapping

Agriculture and Environmental Mapping

Vegetation absorbs light as part of the photosynthesis process.

6H20 + 6C02 + light = C6H12O6 + 6O2


The reflectance pattern of green vegetation in the visible wavelengths is due to selective absorption by chlorophyll, the photosynthetic pigment in green plants. Plant reflectance in the range 700 to 1,300 nm results primarily from the internal structure of plant leaves. It is a well known fact that the spectral shape and reflectance of green vegetation is sensitive to damage.

The reflectance of healthy vegetation increases as we go from the visible to the near-infrared portion of the spectrum at about 700 nm. Various mathematical combinations of the near infrared (NIR) channel and the red channel have been found to be sensitive indicators of the presence and condition of green vegetation. These mathematical quantities are thus referred to as vegetation indices. Vegetation indices may be used as an indicator of relative biomass and greenness. Mapping relative biomass or greenness for harvesting the "cream of the crop."

Spectral Imagery

Near-Infra Red Light




LiDAR

Light Detection and Ranging
 
LiDAR technology involves a scanning and ranging laser system that produces pinpoint accurate, high-resolution, topographic maps. The entire process of airborne laser mapping is highly automated from flight planning, to data acquisition, to the generation of digital terrain models. The basic components of a LiDAR system are a laser scanner and cooling system, a Global Positioning System (GPS), and an Inertial Navigation System (INS).

The laser scanner is mounted within a properly outfitted aircraft and emits infrared laser beams at a high frequency. The scanner records the difference in time between the emission of the laser pulses and the reception of the reflected signal. A mirror that is mounted in front of the laser rotates and causes the laser pulses to sweep at an angle, back and forth along a line. The position and orientation of the aircraft is determined using a phase differenced kinematic GPS. GPS systems are located in the aircraft and at several ground stations within the area to be mapped.

Our company is an outside sales force for the leading providers of high resolution LiDAR data, Aerial Imagery and Satellite Imagery. As an outside sales force we are able to provide the lowest cost for geospatial data. Our unique ability to create GIS data at a county or agency wide level and our successful track record in private and government offices makes us a desirable partner in geospatial projects. Our company’s products and services help define project goals by providing a stepping stone for geospatial project development.

Lidar Example

Laser Scanning Mapping





Surface Modeling

Elevation and Topography
 
Topography refers to the "lay of the land" in terms of elevation, slope, and orientation. Terrain is a similar concept, used more to describe the land itself than the study of it. "Relief" is often used to refer to the third dimension of a map whether in actuality (as in a "raised relief" map, or drawn, as with contours, hachures or shading) or the territory it describes.

The understanding of topography is critical for a number of reasons. In terms of hydrology understanding the topography of an area enables the understanding of watershed boundaries, drainage characteristics, water movement and impacts on water quality.

Watershed Mapping

3D Elevation Modeling



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John Schweisinger