Basic GIS Terms You Should Know

Often we hear people mention some terms in GIS which are aligned to their line of work and we start wondering what they might be saying. Depending on where they placed the word in a sentence some might take a wild guess at what their colleagues are actually saying.

For students, this is quite different because most of the times you are expected to answer questions relating to these words in an examination set up and there is no room for wild guessing.

Today we are going to define some of these key terms that you are supposed to know so that we all understand and can be able to get the meaning of these conversations and instructions.

Glossary Basic GIS Terms

Attribute – A characteristic of a geographic feature, typically stored in tabular format and linked to the feature in a relational database. The attributes of a well-represented point might include an identification number, address, and type.

Base Layer – A primary layer for spatial reference, upon which other layers are built. Examples of a base layer typically used are either the parcels, or street center-lines.

Buffer – A zone of a specified distance around a feature.

Computer Aided Design (CAD) – An automated system for the design, drafting and display of graphically oriented information.

Coordinate – An x,y location in a Cartesian coordinate system or an x,y,z coordinate in a three dimensional system. Coordinates represent locations on the Earth’s surface relative to other locations.

Database – A logical collection of interrelated information, managed and stored as a unit. A GIS database includes data about the spatial location and shape of geographic features recorded as points, lines, and polygons as well as their attributes.

Digital Elevation Model (DEM) – Terrain elevation data provided in digital form.

Digitize – To encode map features as x,y coordinates in digital form. Lines are traced to define their shapes. This can be accomplished either manually or by use of a scanner.

Geocode – The process of identifying a location by one or more attributes from a base layer.

Layer – A logical set of thematic data described and stored in a map library. Layers act as digital transparencies that can be laid atop one another for viewing or spatial analysis.

Line – Lines represent geographic features too narrow to be displayed as an area at a given scale, such as contours, street center-lines, or streams.

Metadata – Information about a data set. It may include the source of the data; its creation date and format; its projection, scale, resolution, and accuracy; and its reliability with regard to some standard.

Ortho Imagery – Aerial photographs that have been rectified to produce an accurate image of the Earth by removing tilt and relief displacements, which occurred when the photo was taken.

Point – A single x,y coordinate that represents a geographic feature too small to be displayed as a line or area at that scale.

Polygon – A multi-sided figure that represents area on a map. Polygons have attributes that describe the geographic feature they represent.

Scale – The ratio or relationship between a distance or area on a map and the corresponding distance or area on the ground.

Spatial Analysis – The process of modeling, examining, and interpreting model results. Spatial analysis is useful for evaluating suitability and capability, for estimating and predicting, and for interpreting and understanding.

Structured Query Language (SQL) – A syntax for defining and manipulating data from a relational database. Developed by IBM in the 1970s, it has become an industry standard for query languages in most relational database management systems.

Theme – An ArcView theme stores map features as primary features (such as arcs, nodes, polygons, and points) and secondary features such as tics, map extent, links, and annotation. A theme usually represents a single geographic layer, such as soils, roads, or land use.

This should get you started. We will be releasing more terms in the posts to come. Learn terms can be quite challenging but bit by bit everyone gets to know in the end.

Source: County of Shasta California

About the Author


Kumbirai is a 4th year Surveying & Geomatics students at the Midlands State University in Zimbabwe. He is also the Founder and Team Lead at African Surveyors Connect. He enjoys spending time writing web-applications and is more of a GIS enthusiast who mainly focuses and grew interests in Health and Land Administrative Applications of Geographic Systems.

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