Meeting review by Richard Teasdale
At the DACS February 2015 general meeting, long-time DACS member, Ed Hicks, gave us a wide-ranging overview of the subject of maps and map-making. The broad theme of Ed’s talk was the revolutionary changes in the world of maps that have been brought about by computers and the internet.
Ed is a mapmaker and the owner of Orienteering Unlimited, Inc., which, from its base in Somers, NY, offers map-making and related services.
The presentation began with a review of some of the reasons why people use maps. There are lots of kinds of maps. Although navigation is the commonest use for maps, few people have been taught how to use a map correctly for that purpose.
Many users of online maps do so through Google but Microsoft’s Bing also has good maps via its Bird’s-Eye service. Bird’s-Eye provides pictures of each location from 4 different directions: north, south, east, and west. Open Street Maps, Mapquest, and Google Earth are other examples of online map websites that are commonly used.
Sometimes maps can give an interesting perspective on how a location has changed over time. Ed mentioned a website which contains historical maps of Westchester county, N.Y., some going back as far as 1881. In the early days, atlases were financed by property owners who wanted their names to appear on the maps. Plots of land whose owners declined to contribute appeared unnamed on the map.
Historical perspectives can also be gotten from websites which provide aerial photographs. (Most so-called “satellite” photos are actually aerial photographs.)
New York State re-photographs about one quarter of the state every 3 years. Connecticut also has a collection of maps and photographs, hosted by UConn’s MAGIC library (http://magic.lib.uconn.edu/).
Ed described some of the standard elements of maps (conventional and digital). He then went on to explain the two main types of image file that digital maps consist of: raster and vector.
He also described the difference between geo-referenced maps and “paper” maps, which basically is the presence or absence on the map of a coordinate system that measures positions on the surface of the earth. The most commonly used coordinate system is latitude and longitude, but there are others.
Maps can indicate three north directions – most people are familiar with two of them: “True” north, which is the direction to the North Pole, and Magnetic north, which is the direction to the north magnetic pole. Since the North Pole and the north magnetic pole are at different points on the earth’s surface, the difference between the two north directions, known as “declination”, varies from place to place. Another complication is that the position of the north magnetic pole is constantly changing. There are various websites, e.g. NOAA, that can be used to determine the declination, given a particular place and time.
Some compasses have the ability to store the declination value so that when they are used with a map, the true north reading is seen automatically and does not have to be calculated manually.
The third north direction, Grid North, relates to the rectangular grid that results from projecting the curved surface of the earth onto the plane surface of a map. The projection unavoidably results in some distortion on the map. Grid north, which corresponds to the edge of most maps, is therefore slightly different from true north.
Ed reviewed the pros and cons of using a GPS device for navigation.
He then discussed cartography, the process of making a map. Traditionally done by hand, maps are now created using one of three types of software: Geographic Information Systems (GIS), Computer-Aided Design (CAD), and specialized illustration software.
The data used to make maps come from a variety of sources. One of the most fascinating of these is the new technology, LIDAR, which is transforming the business of map-making. Light Detection and Ranging is a technique based on the use of lasers, to measure distances to topographical features. Light has a much shorter wavelength than radio waves and so is able to provide much more accurate distance measurements than radar.
Ed described the steps by which Orienteering maps are made, then rounded out his presentation by talking about the sports of Orienteering and Geocaching.
Unknown to many Americans, Orienteering is very popular in Scandinavia (where it originated) and in other parts of Europe. Orienteering contestants use their map-reading skills to navigate from point to point, competing to arrive at the finish line first. Ed described some of the techniques that experienced orienteers use.
Orienteering maps are very detailed and must be accurate and up-to-date. Ed’s company makes many of the orienteering maps used in the Danbury and Westchester areas.
Geocaching is a high-tech treasure hunt that has grown up in recent years, based on the wide use and availability of GPS devices and systems. A geocache is a hidden box whose location coordinates are given on the geocaching website (http://www.geocaching.com/). Treasure hunters use their GPS devices to find the box and record their discovery.
The evening concluded with a Q&A session.