From Earlham CS Department
Jump to navigation Jump to search

Lab Write-up for Group Red

Albert Greene, Lilly Cutler, Emily Van Cise Lab One: Where Am I? Science, Technology, and Society 2/4/2011

Part one: Description and Method

We were charged with exploring the various means of identifying location, and by extension, navigation. To simplify our overall project, we were given a location within walking distance in the epitome of constructs, the prime meridian in Greenwich. Our task was, once provided with a location by our instructor, to identify the coordinates of this point using three different methods available in the modern era. Although humans have developed an impressive array of devices and methods with which to navigate, we chose to utilize three divergent tools. First and the most fundamental is general reason and understanding of the structure which serves as the foundation for the human enterprise of navigation. Our second method was to employ Global Positioning Satellite technology, better known as GPS. Finally, we used a program known as Google Earth, which generates a three dimensional simulation of the earth based on satellite images and computer modeling.

Our use of general logic incorporates a number of assumptions that reflect the fundamental design of latitude, longitude, directionality, elevation and space. We could deduce the latitude by noting that the city of London sits comfortably on the N51* mark, and further, that the Thames is around the 28 minuet mark. The location we were given sat half way between the ends of Greenwich Park, a mile long patch of grass. We could then claim that the latitude of our location was between points 0 and 1000. We determined longitude by measuring the step of one metric Bill whose pace is one meter per step. We counted the calibrated step to determine how far we were from the prime meridian which would give us the longitude. Objects north and south of us could be identified by noting that the sun rises in the east and sets in the west. Given the time, we could note its accent or decent and determine north and south relative to its location in the sky. Finally, given that the Thames is at mean sea level 0, and that the Greenwich observatory is 153 feet high, we could deuce our relative elevation to both points. After looking at our findings utilizing digital and satellite technology, it was surprising how accurate general reason was.

Global Positioning Satellites technology is relatively simple. Given a GPS, a devise that communicates with satellites above, we merely read off and record our location. The satellites, which are in orbit above the earth, cover a circular area and the devise finds our location by identifying the overlap of the areas covered. We were given latitude, longitude, elevation and could place landmarks. The devise can measure the distance between these two points and give us the length in meters.

Google Earth, a program which generates a “perfect” model of the earth is also an incredibly simple method for divining our location. We merely needed to find Greenwich via the search option, find our location specific spot, which was conveniently marked as a point of interest. Moving the cursor over the point would give us latitude, longitude and elevation. The program also includes a measure function and provides a wide array of measurements for points you place on the map. Using these three methods we were able to find out where the heck we were.

Part two: Description of Location

We were told to orient ourselves on the steps of Our Lady Star of the Sea Church (see below). A Catholic Church located on Crooms Hill Road in Greenwich, London. The road runs parallel to the Greenwich park grounds on the West side up a steep incline. Down the hill, to the north we saw a white house with metal guardrails on the roof. To the south, up the hill, we could see a red brick house with white trim just past a grassy noel. Across the street, toward the prime meridian was another incline fenced off by a metal gate and thick shrubbery. This barrier was a big reason for having a margin of error greater than ten meters with our measurement of calibrated stride. All that remains to be said at this point is that the area is lovely and that you can find more information on the church at http://www.portcities.org.uk/london/server/show/conMediaFile.5351/Our-Lady-Star-of-the-Sea-Church-Crooms-Hill-Greenwich.html.

Part Three: Tabulation of findings:

GPS- N. 51 28.585 +/-5-6m
Google Earth- N 51. 28 349
Reason- N 51. 28. (000-1000)

GPS- W. 000. 00 346 +/-5-6m
Google Earth- W 000 00. 352
Reason- W 000 00.360 +/-

GPS- 37m
Google Earth- 37m
Reason- 38.25

Distance from Prime Meridian
GPS- 428 m
Google Earth- 417m
Reason- 360m

Part Four: A Discussion of Error

In terms of general logic we used our knowledge of location to determine our latitude. We already knew our approximate location. We generally guessed where we were, but were unable to know exactly where we were in terms of latitude, elevation, and longitude. We used a calibrated step, so this was not a perfect measure of distance. In terms of GPS, it is accurate up to five or six meters. So we know we were accurate up to five or six meters. In terms of Google Earth, the cursor placement could be relative and is not necessarily completely accurate with the location.

Part Five: Raw Data

GPS coordinates
Longitude W. 000. 00 346 +/-5-6m
Latitude N. 51 28.585 +/-5-6m
Elevation 38m
Distance from meridian: 428m

Google Earth
Longitude: W 000 00. 352
Latitude N 51. 28 349
Elevation 111 feet 37 m
Distance from prime meridian : 417m

General Logic
Latitude: N 51. 28. (000-1000)
Longitude: number of M. from meridian. W 000 00.360 Distance from meridian# of steps x 1 step360+- 15 steps
Average rate of bill+ 1 m
Elevation halfway up Cromwell hill from the Thames which is +5 m from sea level, 153 feet at top of hill, or 46m somewhere between 10 m probably 153 div 3=51 mult .75= 38.25 m above sea level

What is north: White house with metal guard rail on roof
What is south: red house on hill with white trim

Path taken during calibrated measurement march:

Reviewed - 21 February 2011