The magazine of the Melbourne PC User Group The New Face of Cartography and Maps Major Keary |
Cartography is defined as 'the drawing of maps and charts'; on land one uses a map, but at sea and in the air one uses a chart. The terms, map and chart, imply the use of a projection, which takes account of the fact that Earth is a spheroid and adjustments are required to represent the whole or a part on a flat sheet of paper. When, for example, a land development is surveyed the resulting document is usually called a plan — it does not make any adjustment for curvature.
A cartographer usually works with data provided by other people. In the present era most of that data comes from satellite imagery or aerial photography, but in days of old people worked on-the-ground to gather geographical information and usually recorded it in the form of a map or chart that, in turn, often became the data from which a cartographer worked. It was common for the primary map makers to employ celestial navigation for position fixing.
The arrival of two new books on mapping reminded me of the immense changes that have affected cartography and navigation since I was first involved with them just over half a century ago. It was a time when celestial navigation was a craft and cartographers were generally found in a navy hydrography office, army survey corps, or some government department to do with survey and mapping. Part-time map makers, some of whom were highly talented, filled many a blank area on maps and charts of the day. Their efforts required patience, familiarity with several disciplines, and a knowledge of the instruments. I still have a theodolite — manufactured in Showa thirteen (1939) for the Japanese army — that now sits most of the time as an ornament alongside a New Guinea coastal master's licence issued in 1961. The sextant is usually associated with navigation at sea, but was widely used on land for triangulation and measuring distance, and on water for charting coastlines by triangulation.
Until the wide availability of computers and specialised software nearly everything from computations to drawing a map or chart was manual, and Morse transmissions from WWV were the source of precise time. It would be hard to find a contour pen today, or even a set of haversine tables. Aerial and satellite imagery has done away with on-the-ground work that used to be the backbone of mapping, especially in remote areas. The fundamental science of map projections, however, does not appear to have changed — but some of the familiar names, such as Bonne, Cassini, and Lambert seem to have passed into history.
A body of computer-based technologies has been developed for cartography and the use and distribution of maps, complete with its own vocabulary. Geospatial doesn't appear in any of my dictionaries, but one trips over it frequently in modern mapping literature. A Web search found just one entry contained in Webster's New Millennium Dictionary of English (Preview Edition (v 0.9.6) Copyright 2003-2005):
| Main Entry: | geospatial | |
| Part of Speech: | adjective | |
| Definition: | pertaining to the geographic location and characteristics of natural or constructed features and boundaries on, above, or below the earth's surface; esp. referring to data that is geographic and spatial in nature. |
A simple Web search on 'geospatial' throws up many pages, including vendors of
geospatial software, 'careers in ...' and even the Geospatial Intelligence
Agency; but none of them seem to define the term.
There is also the usual flock of acronyms, initialisms, and abbreviations, such
as:
|
GIS OGC OGR OGF GDAL GMT GNIS ESRI |
Geographic Information Systems, OpenGIS Consortium, OpenGIS Simple Features Reference Implementation, Open GRASS Foundation, GRASS Geographic Resources Analysis, Support System, Geospatial Data Abstraction Library, Generic Mapping Tools, Geographic Names Information System, Environmental Systems Research Institute. |
Maps also have their own raster formats. A visit to
http://www.gdal.org/format_list.html threw up some forty formats over and above GIF, TIF, JPG, and
PNG.
The exponential growth in map usage is, no doubt, due to the availability of
material in digital form, especially on the Web, and the software that makes it
possible to create a plethora of different outputs. The ubiquitous Global
Positioning System (GPS) has also added to the demand for maps — having raw
latitude and longitude is not much good if one can't locate it on a map.
Apart from wayfinding, maps are now used extensively in the presentation of
information. For example, a map can be added to an Excel spreadsheet with
MapPoint, another Microsoft
product; and Excel spreadsheets can be geo-enabled (described in Mapping Hacks
[O'Reilly, ISBN 0596-00703-5I) and the necessary VBA macro can be
found at
http://www.mappinghacks.com/data/spreadsheet/geodata_sample.xls, with further information at
http://nmml.afsc.noaa.gov/Software/ExcelGeoFunctions/excelgeofunc.htm.
It is not surprising that Web technologies have been adapted to — and new ones
developed for — map storage, retrieval, and viewing. However, the sheer volume
of map-related data can be an impediment to finding what one wants, and not all
custodians of mapping and related imagery make it easy — or even possible — for
general users of the Web to find, view, and download data.
A co-author of Mapping Hacks, Schuyler Earle, comments that "... slowly but
surely, cartography is shifting from being a traditionally read-only medium to
most people, and into becoming a read/write medium". His use of the terms, 'read
only' and 'read/write', succinctly reflect the change in a way that few other
words could.
Reprinted from the March 2006 issue of PC Update, the magazine of Melbourne PC User Group, Australia
