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Carto-Jargon 201: Cartography Terms Defined

In a previous blog post, we defined a few common cartography terms that you might be likely to encounter while using MAPublisher and Geographic Imager; however, that was just the tip of the iceberg when it comes to cartography and GIS jargon. Here, in no particular order, are several additional terms used by cartographers, GIS professionals and people who work with spatial imagery.

Topology

Topology is a key principle in GIS for data management and integrity, ensuring the data quality of spatial relationships is maintained. In general, a topological data model defines how spatial objects (point, line, and area features) are represented, and defines and enforces data integrity rules (for example, there should be no gaps between polygons).

Azimuth

The horizontal angle, measured in degrees, between a baseline drawn from a center point and another line drawn from the same point. Normally, the baseline points true north and the angle is measured clockwise from the baseline.

Neatline

All 2-dimensionally rendered maps have to compromise somewhat on accuracy, even if only just a little by moving or scaling features to improve readability. However, the neatline is never adjusted, making it the most accurate element on a map.

The neatline is the border defining the extent of geographic data on a map and separating the body of the map from the map margin. It demarcates map units such as meridians and parallels, and depending on the map projection and the units selected, the neatline may not have 90-degree corners.  

Geodatabase

A Geodatabase, a database or file structure used primarily to store, query, and manipulate spatial data, stores geometry, a spatial reference system, attributes, and behavioral rules for data. An advantage of geodatabases over shapefiles is that various types of geographic datasets can be collected within a geodatabase, including feature classes, attribute tables, raster datasets, network datasets, topologies, and many others.

Geoprocessing

Geoprocessing is an operation used to manipulate a GIS data resulting in a new set of data. Common geoprocessing operations include geographic feature overlay, feature selection and analysis, topology processing, raster processing, and data conversion. Geoprocessing allows for the definition, management, and analysis of information used to make decisions based on patterns within the GIS data.

Shapefile

An Esri Shapefile is a vector data storage format for storing the location, shape, and attributes of geographic features. A shapefile is stored as a set of related files and contains one feature class. An alternative to using shapefiles to store GIS data is a geodatabase, however, shapefiles have some advantages in terms of relative simplicity and wide-ranging compatibility with many applications. Related files contain additional information that is read by the shapefile when opening/importing in GIS applications, as long as these related files have the same name and reside in the same directory – the *.dbf (database) file contains attribute information, and the *.prj (projection) file contains coordinate system information. Shapefiles also have limitations such as the inability to support raster files, and large file sizes.

Buffer

A zone around a map feature measured in units of distance or time is called a buffer. Buffers are useful for proximity analysis.

Geodesy

Geodesy is the science concerned with the measurement and mathematical description of the size and shape of the earth and its gravitational fields. Geodesy includes the large-scale, extended surveys for determining positions and elevations of points, in which the size and shape of the earth must be taken into account to achieve accuracy.

Vector vs Raster

The terms vector and raster are encountered often in cartography though they are not often defined. In a nutshell,

Raster data is made up of pixels (sometimes referred to as grid cells). Each pixel can have a range of values used to represent data points. For example, in a satellite image, every pixel has a red, green and blue value.  

Vector data is not made up of a grid of pixels. Instead, vector graphics are comprised of vertices and paths where the vertices are x,y coordinates. In GIS systems, they are a latitude and longitude with a spatial reference frame.

Mosaic

A Mosaic is a single raster dataset composed of two or more merged raster datasets—for example, one image can be created by assembling multiple aerial photographs whose edges usually have been torn or cut selectively and matched to the imagery on adjoining images to form a continuous representation of a portion of the Earth’s surface.

Orthorectification

The process of correcting the geometry of an image so that it appears as though each pixel were acquired from directly overhead. Orthorectification is used to correct terrain distortion in aerial or satellite imagery.

Sources

http://wiki.gis.com/wiki/index.php/GIS_Glossary/
https://legacy.lib.utexas.edu/maps/glossary.html
https://gisgeography.com/spatial-data-types-vector-raster/

Carto-Jargon 101: Cartography Terms Defined

The field of cartography is filled with jargon and terminology that can pose a challenge for newcomers learning to use mapping software such as MAPublisher to make beautiful maps, and those who don’t have a formal background in cartography. It also doesn’t make it easier when different software packages have their own variations on certain terms. To help the cause, we have compiled a short list of common cartography terms or “carto-jargon” that you may encounter while using MAPublisher or Geographic Imager.

Basemap

A basemap is a background image which can include aerial imagery, topography, terrain and streets and other fundamental layers and is used as a starting point to create a new map. The basemap is georeferenced and is usually the most accurate source of spatial information within the data system that makes up the finished map. Additional layers of data such as labels, symbols and paths are then added to the basemap to create the final product.  

Feature

Any real-world object that is represented on a map is a feature. Features can encompass large areas of a map, such as bodies of water and mountain ranges, or they can be discreet objects like parking areas, public washrooms or fire hydrants.

Attribute

Attribute data is information about spatial features and is stored in tables. It is also the information that specifies the appearance and labeling of features on a map. For example, the graphic attributes of a river might include the thickness of the line, line length, color, and the name used for labeling.

Control Point

A control point is a location on the map with known pixel (x,y) coordinates. Control points are used in georeferencing to allow for extrapolation of the relative location of other points whose exact coordinates may not be known.

Coordinate System

A coordinate system is a reference system used to represent the locations of geographic features on a map. It provides the basis for identifying locations on the earth’s surface. There are thousands of different coordinate systems, most of which are limited in use to highly specialized purposes.

Projection

The earth is not flat and so imagining that it is for the purpose of putting it on a 2-dimensional map results in some distortion. A projection is a method by which the curved surface of the earth is portrayed on a flat surface and is based on a mathematical transformation of the earth’s lines of longitude and latitude onto a plane. There are many different projections, each of which distorts distance, area, shape, and direction is some way, therefore no projection can result in a perfectly accurate flat map. Check out the Avenza Projections Guide for a more detailed information.

Georeferencing

Georeferencing involves aligning geographic data to a known coordinate system so it can be viewed, queried, and analyzed relative to other geographic data on the same map. Georeferencing may involve shifting, rotating, scaling, skewing, and in some cases warping, rubber sheeting, or orthorectifying the data to improve accuracy.

Graticules and grids

Graticules are the network of longitude and latitude lines on a map or chart that relates points on a map to their true locations on the earth. You can think of this a grid system – in fact, the terms are sometimes used interchangeably, but there is a subtle difference. Graticules are derived from 3-dimensional ellipsoidal shape of the earth and are formed by the the lines of latitude (parallel lines circling the earth), and lines of longitude (non-parallel lines converging at the earth’s poles). A grid system is comprised of a set of parallel and perpendicular lines that are superimposed on a flat projection of the earth, creating an x,y coordinate system. An example of a grid system is the Universal Transverse Mercator (UTM) system.

Themes

In MAPublisher, MAP Themes are a collection of thematic cartography tools designed to automate how styles and symbols are applied, charts are produced, and data is plotted. There are three themes which you can be customized to suit your needs: Stylesheet, Chart, and Dot Density. MAP Themes offer a lot of flexibility as they can be edited, applied, duplicated, automated, exported, and cleared without affecting the spatial referencing of map features.

This is just a small sampling of the more robust glossary of terms available in the our MAPublisher and Geographic Imager documentation packages.

Sources
http://www.avenza.com/help/mapublisher/10.1/index.html?whats_new_in_mapublisher.htm
http://www.avenza.com/help/geographic-imager/5.3/index.html?glossary.htm
https://www.gislounge.com/gis-dictionary/
http://geography.name/gridgraticule/