Before reliable timepieces were available, astronomers were able to determine longitude only by careful observation of recurring celestial events, such as eclipses of the moons of Jupiter. If positions are measured relative to other positions, what is the first position measured relative to? The answer is: the stars.
![point to point measure point to point measure](https://www.venacavadesign.co.uk/shopimages/products/extras/516-extra-4.jpg)
You might wonder how a control network gets started. Vertical control points however, were established by the technique of spirit leveling which is more suited to being conducted along gradual slopes such as roads and railways that seldom scale mountain tops. horizontal stations were often located on high mountains or hilltops to decrease the need to construct observation towers usually required to provide line-of-sight for triangulation, traverse and trilateration measurements. In the U.S., the National Geodetic Survey (NGS) maintains a National Spatial Reference System (NSRS) that consists of approximately 300,000 horizontal and 600,000 vertical control stations (Doyle,1994).ĭoyle (1994) points out that horizontal and vertical reference systems coincide by less than ten percent. In 1988 NGS established four orders of control point accuracy, ranging in maximum base error from 3mm to 5cm. Land surveyors measure horizontal positions in geographic or plane coordinate systems relative to previously surveyed positions called control points, most of which are indicated physically in the world with a metal “benchmark” that fixes the location and, as shown here, may also indicate elevation about mean sea level (Figure 5.10). Positions on the globe, for instance, may be specified in terms of angles relative to the center of the Earth, the equator, and the prime meridian. Geographic positions are specified relative to a fixed reference. The techniques and tools of conventional surveying are still in use and, as you will see, are based on the very same concepts that underpin even the most advanced satellite-based positioning. Yet, none of the power or capabilities of GPS would have been possible without traditional surveyors paving the way.
#POINT TO POINT MEASURE UPDATE#
This is what a rocket launch looks like from about 120 miles away and I know that distance thanks to the Maps app in Windows 10.īe sure to check out all of our Windows 10 Anniversary Update Coverage.īut, wait.there's probably more so be sure to follow me on Twitter and Google+.Ease, accuracy, and worldwide availability have made ‘GPS’ a household term. That second set of points, the ones on the right, showed me I was about 120 miles away as the crow flies. Augustine Beach, and I wanted to know how much closer I was than normal.
![point to point measure point to point measure](https://i.pinimg.com/originals/45/ba/a5/45baa5fc48b2acd0d03b399ddb5b8b0f.jpg)
Well last night I watched a Delta IV launch from Cape Canaveral at a new location, the fishing pier in St. Normally I watch launches from nearby my house which is about 150 miles, the left set of lines shown above, from the launch site at Cape Canaveral. The reason I have those two sets of points in this example relates to doing photography and watching rocket launches as I mentioned earlier.
![point to point measure point to point measure](https://img.gadgethacks.com/img/98/02/63637268200670/0/use-google-maps-measure-distance-between-2-more-points.w1456.jpg)
The Measure distance tool will then display the distance between those two points directly on the map next to the line you just drew.Īs you can see it is also possible to measure the distance between more than one set of points on a map. This feature was very useful for me in the last 12 hours as I combined two of my hobbies, photography and watching rocket launches, and then wanted to know approximately how far away I was from the launch site at Cape Canaveral.įirst let's take a look at how you use the Maps app to get the distance between two points.Īfter opening the Maps app, just search the Start Menu for Maps, look in the upper right hand corner of the app window for the toolbar.ġ - Select this icon to open the Windows Ink Toolbar.Ģ - Select this icon to turn on the measure distance featureģ - If you do not have a pen or stylus then select this icon to use your finger to draw on the mapĪt this point you just need to make sure the two points you want to measure the distance between are visible on the screen and then simply draw a direct line from Point A to Point B. The updated official Maps app on Windows 10 integrates one of the big new features in the Windows 10 Anniversary Update, Inking, into its set of tools and one of those options is the ability to draw a line between two points and find out what that distance is.
![point to point measure point to point measure](http://typography101.net/images/measurement.jpg)
This is often referred to the distance as the crow flies. Sometimes it can be very handy to know the direct distance between two points on a map otherwise.