Jul
20
2010
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What are Deadly Maps and Evasion Charts?

lucia-mapDeadly Maps and Evasion Charts are just two of the very many types of maps referenced on a website that is a gold mine for map searchers, that of the Dudley Knox Library at the Naval Postgraduate School. The well sorted website provides links to a great many websites for current and historical maps as [more…]

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Jul
19
2010
2

What are Operational Navigation Charts and Tactical Pilotage Maps?

hainan-onc84Operational Navigation Charts (ONC) and Tactical Pilotage Maps (TPM) are large 42” x 57.5” topographical maps prepared and published by the US Defense Mapping Agency Aerospace Center in St. Louis, Missouri, for flight navigation. There are now, of course, digital devices and CDs that pilots use, which can be updated easily. But most of us [more…]

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Jun
24
2010
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What are County Land Ownership Maps?

land ownership map Knox County IllinoisLand ownership maps are an important resource for researching your ancestors in the United States. The most useful ones for researching your family history were created between 1860 and 1918 when America was being opened up to settlers and the railroads. As the name suggests, the majority of maps were drawn up to show land [more…]

Mar
19
2010
1

If I dug a hole through the center of the earth, where would I come out?

digging-a-hole-through-the-earthMany parents have convinced their youngster that the earth is not flat, but rather a sphere, only to be asked “So what’s on the other side of the earth?” American parents are likely to answer “China”. Maybe British parents reply “Australia” or “New Zealand”, and parents “down under” reply “England” or “Europe”. Then the youngster [more…]

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Mar
06
2010
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What is great circle navigation?

great-circleGreat circle navigation is following the shortest route between two points on a sphere, the earth in this case. A great circle on any sphere is one that divides it in two equal halves: the equator, any longitudinal line through the poles, or any similar circle that has its center at the middle of the [more…]

Jun
24
2009
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What is the CIA World Factbook?

CIA World Factbook 1995 cover (PD)The United States Central Intelligence Agency (the CIA), was created in 1947 to provide senior US policymakers with information related to national security. The CIA collects information (“intelligence”), correlates it in relation to national security, and disseminates it appropriately. Here’s what the CIA says about itself on its Kids’ Page: The CIA is an independent [more…]

Mar
26
2009
1

What free services does Google provide (besides search)?

Google Bus (photo by bradleypjohnson - CC-BY)Everyone knows that Google is a search engine, but many people are unaware of just how many other free services are offered by Google. For some people, Google’s web services can completely replace the application software installed on their computer. Here are some of the things that Google can do for you, at no cost: [more…]

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Mar
24
2009
1

What is geocaching?

Typical contents of a geocache (photo by Paul Downey - CC-BY)Geocaching is the recreational activity of hunting for a hidden cache of “treasure” using a GPS receiver. Using the published co-ordinates of the cache, and perhaps a simple clue, you find your way to the designated location to discover a small container containing the “treasure”. There are hundreds of thousands of geocaches hidden all over [more…]

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Mar
24
2009
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How does the GPS navigation system work?

Around the world, making an artistic GPS track (graphic by Oliver Belikan - CC-BY)GPS, the Global Positioning System, can determine your location anywhere on the earth. In good conditions the accuracy is just a few meters. How can GPS do this? The GPS system uses a constellation of over 24 satellites orbiting the earth. The orbits are arranged so that several satellites are “in view” at any time, [more…]

Jan
31
2009
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What is a map measurer?

Map Measurer (photo by ndrwfgg - CC-BY)A map measurer is also known as a map wheel, an opisometer, or a meliograph. It is used to measure the length of routes or features on a map. You use a map measurer by dragging the small wheel along the surface of the map, following carefully the path of the line that you wish [more…]

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