Types of Topographic Maps

History

· Maps have been used since ancient times to depict land boundaries for tax purposes. The Romans, who built extensive road systems, mapped their empire. The Dutch mathematician and geographer Reiner Gemma Frisius developed the practice of triangulation to document the land. The first topographic map of a nation was of France, complied by the Cassini family and called "Carte de Cassini," published in 1793. In the United States, President Thomas Jefferson began mapping the eastern coastline while explorers and the Army Corps of Topographical Engineers documented the rest of the country. The United States Geological Survey was established in 1879 to compile and complete the data.

Features

· There are two types of features contained on a topographic map: cultural and natural. Cultural features include roads, buildings, cities, railways, power lines and boundaries. Natural features are broken down into four categories: water, relief, vegetation and toponymy. Water includes rivers, lakes, streams, swamps and rapids; relief includes mountains, valleys, slopes and depressions; vegetation refers to wooded and cleared areas, vineyards and orchards; and toponymy is simply the names of the aforementioned features.

Scale

· Every topographic map has a scale, the most common being 1:24,000, or one inch equals 24,000 inches or 2,000 feet of land. Topographic maps vary in size because of the varying size of longitude lines closer to the equator. Topographic maps of the entire United States are 23 inches by 27 inches for latitudes below 31 degrees and 22 inches by 27 inches for higher latitudes. The larger the area of the map, the less detail you will see.

Colors

· Each feature is shown in a specific color so there is less confusion. There are generally eight colors present on a topographic map: black, red, orange, brown, blue, green, grey and purple. Minor roads and highways, buildings, railways and power lines are black, major highways and urban developments are red, orange represents unpaved roads, brown is for contour lines, blue represents water, green shows vegetation, grey is used for words on the back of a map and purple shows updates or recent additions.

Symbols

· As often as possible, symbols look like what they represent when viewed from the air. An example of this is the outlines of various buildings. There is a glossary and a key that shows what various symbols mean in grey on the back of topographic maps. Some symbols are universal, such as black tracks with lines through them for railways.

Types of Topographic Maps

By Lori D. Fairchild, eHow Contributor , last updated April 25, 2012

Topographic maps are 2-D maps that show elevation through a series of contour lines. Lines placed closer together indicate steeper areas while more distance between lines indicates a flatter area. You can use the maps when planning hiking, hunting or fishing trips or when deciding if land is appropriate for development. Topographic maps come in various sizes and scales. The larger the size, the more area you can typically see on the map.

Minute Quads

o These topographic maps cover an area measured by 7.5 minutes of longitude and 7.5 minutes of latitude. The 7.5 minute quad maps that are created by the U.S. Geological Survey have a scale of 1:24,000, where 1 inch is equal to 24,000 inches or 2,000 feet. These maps cover the smallest area and show the most detail. Engineers, city planners and people interested in outdoor recreation will find these maps the most useful.

Minute Quads

o The 15-minute quad maps cover four times the area of a 7.5 minute quad map. They cover 15 minutes of longitude by 15 minutes of latitude. These maps generally contain a scale of 1:62,500, where 1 inch equals 62,500 inches or about 5,208 feet. Generally, planners use these maps for land management.

Degree Sheet

o The 1-degree sheet map covers 1 degree of longitude and 30 minutes of latitude. Eight 15-minute quads will fit in the 1-degree sheet. The typical scale for the 1-degree sheet is 1:100,000, where 1 inch equals 100,000 inches or about 8,333 feet. People use maps of this scale in state and regional planning.

Degree Sheet

o A 2-degree sheet holds an area of 2 degrees of longitude and 1 degree of latitude. This is typically the largest type of topographical map. A 2-degree sheet will hold four 1-degree sheets. These maps usually have a scale of 1:250,000, where 1 inch equals 250,000 inches or about 20,833 feet. These maps show the largest area with the least degree of detail. They offer a broad look at an area and are useful in regional planning.

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Did You Know?

No-one knows the exact date when the first map was created. However, we do know that down through the centuries, maps have been written in all sorts of ways and on all sorts of materials. Below are some facts about our maps of the Past.

- Maps were written in all sorts of ways and on all sorts of material. Clickhere to find out more.

- In 1973 two maps from the second century B.C. were found in China. One of these was a topographic map, the other was military. They were both written on silk. Do you think it would be difficult to draw a map on silk?

- Eskimos used driftwood, bone and pebbles to represent routes or trading grounds.

- Early maps were often local, showing people where things were within a limited area.

- In the past, maps were often used by abbeys and also the estates of wealthy landowners.

- Some of the first detailed maps of places were made by armies.

The Manufacturing
Process

The production of an accurate topographic map is a long and complex process that may take as much as five years from start to finish. It takes a skilled team of surveyors, engravers, fact checkers, printers, and others to produce a good map. Here is a typical sequence of operations used by the U.S. Geological Survey to produce a 7.5 minute quadrangle topographic map.

Date: 2015-12-11; view: 1438