tmackinnon.com » maps

Geographic Information Systems (GIS)

tmackinnon — Mon, 03 Mar 2008 02:55:42 +0000

Geographic information systems commonly known as GIS has become a rapidly growing technological field that allows Geomatics Specialists to solve and model real world situations by incorporating digital spatial and associated tabular data. It is often defined as a comprehensive computerized information system made up of hardware, specialized software, spatial data and people to help manipulate, analyze and present the information used for storing, manipulating and analyzing spatially indexed information.

GIS operates on many levels and over the past decade has become an essential tool for most urban and resource planning and management organizations. On the most basic level, GIS can be used for simple digital cartography, to create various types of maps.

However the real power of GIS is through its abilities to use both spatial and statistical methods to analyze attribute and geographic information together. The end result of such an analysis can be vast amounts of derivative information, interpolated information or prioritized information.
Geographic information systems commonly known as GIS has become a rapidly growing technological field that allows
Geomatics Specialists to solve and model real world situations by incorporating digital spatial and associated tabular data. It is often defined as a comprehensive computerized information system made up of hardware, specialized software, spatial data and people to help manipulate, analyze and present the information used for storing, manipulating and analyzing spatially indexed information.

GIS technology can be used for scientific investigations, resource and utilities management, modeling, assessments, development planning, cartography and route planning and many other applications.. Some of these and other aspects of the GIS field are currently covered on this web site including projects related to spatial database modeling, Geostatistical spatial modeling, mobile mapping, cartography, and interactive web mapping.

Below are some examples of GIS from a few of the many GIS based projects that I have been involved with over the past few years. The links are to PDF versions of papers, presentations and or manuals related to GIS, I have many more, if anybody is interested in a particular topic then feel free to let me know, as I may have a document available related to that topic.

Examples of GIS

MacKinnon E (2004) Spatial GIS Vegetation Database and GIS Spatial Modeling at Kejimkujik National Park and Historic Site.
MacKinnon E (2003) Mobile Mapping Application for Updating AGRG Weather Station data
MacKinnon E (2003) Mobile Mapping Application – for Updating AGRG Weather Station data
MacKinnon E, & Murphy J. (2003) Leica GS20 Professional Data Mapper – Leica GS20 AGRG Users Guide

GIS Directory
GIS Dictionary
What is GIS – power point presentation with more information about GIS
GIS Theory - an Overview of GIS by The University of Melbourne
GIS.com GIS portal site by ESRI
Geomatica GeoCapacity
Spatial Databases – models of reality

Geomatics – Cartography

tmackinnon — Fri, 22 Feb 2008 03:08:21 +0000

Cartography or Map Design is the practice of creating maps or visual representations of a surface, as you would see it from above it. Traditionally maps have always been created using pen and paper, but since the introduction and wide spread use of geographic information systems (GIS) and computers, cartography practices have evolved more into the digital world. Most maps today are now generated using map software that falls into one of three main types; GIS, CAD, and specialized map graphic design software.

Cartography | Basic Overview

A map utilizes a variety of colors, symbols, and labels to represent actual features and provide information on their existence, location, and the distance between them. It can also indicate variation in terrain, heights of natural features, and the extent of vegetation cover.

Maps often function as visualization tools for spatial data which is acquired from actual measurements and can be stored into a database, from which it can be later extracted for a variety of purposes. Current trends in this field are moving away from traditional methods of map making and toward the creation of increasingly dynamic, interactive maps that can be manipulated digitally, often known as
Web GIS.

Most maps will contain a scale parameter that will allow the user to convert distance on the map to distance on the ground or vice versa. The ability to determine distance on a map, as well as on the earth’s surface, is an important factor in GIS and the spatial relationships between features. Other important key elements or features that you should find on a good map would be a title, a data frame, a legend, a scale bar, a north arrow, and citation information such as the date, the creator, projection, overview map location etc.

The Map on the right is a to scale representation of one of the camp grounds located at Kejimkujik National Park

in Nova Scotia. It was created from survey data collected with a Leica RTK system and a Leica Total Station. The legend is hard to see in this screen grab (actual map poster was 2ft by 4ft) but the red line represents the road, dotted lines are trails and the green polygons are the actual camping plots.

Below are some examples of Maps that I have generated for various projects that I have worked on or have had some involvement in, included are the date and the title of the map with a brief description. Clicking on the link will open up an image of the map with some details about the project (Note: most of these maps were plotted out on large paper sheets for display so some details were lost while generating these miniature image versions for the web site – also some of these are still on display at various places).

Examples of Cartography & GIS Map Products

MacKinnon E (2000) 8th International Marathon Canoe World Championship Site Map - designed for the International Marathon Canoe World Championship that were held in Dartmouth, Nova Scotia
MacKinnon E (2003) AGRG Annapolis Valley LIDAR Ground Validation Campaign - presented at the Geomatics Atlantic 2003 Conference held at Acadia University in Wolfville, Nova Scotia and posted at the Applied Geomatics Research Group seminar room in Middleton, Nova Scotia
MacKinnon E (2003) Jeremy’s Bay Campground, Kejimkujik National Park - campground was surveyed in 2003 and mapped for Parks Canada MacKinnon E (2003)
Jim Charles Loop of Jeremy’s Bay Campground, Kejimkujik National Park - campground was surveyed in 2003 and mapped for Parks Canada MacKinnon E (2003)
New Brunswick High Precision Network and AGRG 2003/2004 LIDAR Zones - presented at the Geomatics Atlantic 2003 Conference held at Acadia University in Wolfville, Nova Scotia and used during the ground validation survey in New Brunswick

Cartography Directory

International Cartographic Association (ICA)
Map Projections
Google online maps with spatial search capabilities
Map Quest online maps with detailed directions
MSN Virtual Earth – Microsoft version of Google Map
Web Cartography

Digital Terrain Modeling – Aspect models

tmackinnon — Tue, 28 Mar 2006 19:08:39 +0000

In digital terrain modeling the Aspect of a surface refers to the direction (azimuth) to which a slope face is orientated. The aspect or orientation of a slope can produce very significant influences on it, so it is important to know the aspect of the plane as well as the slope. Together the slope combined with the aspect of the surface can virtually define the surface plane completely in digital terrain modeling.

Aspect is measured in degrees (similar to a compass bearing) clockwise from magnetic north. A surface with 0 degrees Aspect would represent a north direction, an east facing slope would be 90 degrees, a south facing slope would be 180 degrees and a west facing slope would be 270 degrees.

The example shown to the left (for larger image click here) is a raster aspect model of Lismore, Nova Scotia was derived from a digital elevation model (DEM) calculated using PCI Geomatica remote sensing software. It is represented with a grey scale color ramp and helps to indicate what direction slope faces are orientated.

The image above is of an actual bedrock cliff with some technical information embedded onto the image to help better understand slope and aspect relationships. The black arrow represents the slope or the measured angle that the rock is dipping towards.

The aspect is the orientation that the arrow (slope) is pointing with respect to North, therefore the aspect for this slope would be in an easterly direction and often represented by 90 degrees. The blue arrows represent the X, Y and Z dimensions that the combination of both the slope and aspect would use to represent the terrain features.

Example of an Aspect Map

tmackinnon — Mon, 27 Mar 2006 00:06:02 +0000

The image below is an Aspect Model that I derived from a digital elevation model (DEM) of Lismore, Nova Scotia. The aspect values of the slopes of the DEM are represented in the model by a 0-255 grey scale color ramp. Click here to learn a little more about Aspect Models and how the image below was created.

Slope

tmackinnon — Mon, 27 Feb 2006 18:39:10 +0000

The slope or the gradient of a straight line within a Cartesian coordinate system is known as the measure of how steep a line is relative to the horizontal axis.

In calculations; it is generally represented by the letter m, and defined as the change in the Y coordinate divided by the corresponding change in the X coordinate, between two distinct points on the line (X1, Y1 and X2, Y2). Since the Y axis is vertical and the X axis is horizontal by convention, slope is often referred to as the rise over the run or the change in the vertical coordinates, divided by the change in the horizontal coordinates.

Basically, the larger the slope value, the steeper the line is. A horizontal line has a slope of 0, a 45 degree line has a slope of 1, and the slope of a vertical line is typically undefined. In trigonometry two lines are considered to be parallel if and only if their slopes are equal or if they both are vertical and therefore undefined. Two lines are considered to be perpendicular if and only if the product of their slopes is -1 or one has a slope of 0 and the other is vertical and undefined.

There are two common ways to describe slope. One method is to use the angle of the slope in degrees (0 to 90), and the other is to represent the slope as a percentage (0 to 100). Expressing slope as a percent is common but can be confusing because a percent slope can be greater then 100%. A 100% slope is actually only a 45 degree angle due to the fact that the rise and run of a 45 degree angle are equal and when divided always equals 1 and when multiplied by 100 will equal 100%.

In terrain modeling we generally model an entire surface and not just one line so we need to calculate the slope of a best fit surface plane (which is made of lines). Because the terrain model is usually continuous across the entire surface, it is important to be able to calculate how to represent grid cells (or pixels) when going from one elevation to the next. To do this we generally need to know the aspect or the direction that the surface plane is sloped as well. Together the slope combined with the aspect of the surface can virtually define the surface plane completely.

In the example shown to the left, a slope map of Lismore, Nova Scotia was derived from a digital elevation model (DEM) calculated using PCI Geomatica remote sensing software. It is represented with a grey scale color ramp therefore the color white represents a 0 slope and the shades of grey increase through to black which represents an undefined slope. The majority of slopes for this map do not exceed 17 degrees (except for vertical slopes) as this is a relative low lying area of Appalachian terrain.

The image above and to the right is of an actual bedrock cliff with some technical information embedded onto it so it may be used to help better understand slope. The black arrow represents the slope or the measured angle that the rock is dipping towards. The slope in the image would be 45 degrees approximately so the slope would be 1 or 100%. The rise and the run of a slope with a 45 degree angle will always equals 1, thus when multiplied by 100 to calculate percent slope will equal always equal 100%.

Example of a Slope Map

tmackinnon — Sat, 25 Feb 2006 19:10:27 +0000

The image below is a Slope Model that I derived from a digital elevation model (DEM) of Lismore, Nova Scotia. The values of the slopes of the DEM are represented by a 0-255 grey scale color ramp, therefore the color white represents a 0 slope and the shades of grey increase through to black which represents an undefined slope. The majority of slopes for this map do not exceed 17 degrees (except for vertical slopes) as this is a relative low lying area of Appalachian terrain.

Click here to learn a little more about Slope Models and how the image below was created.