Digital map paper

1) What are the different formats? What do they mean? See the link below for help.

https://www.reddit.com/r/explainlikeimfive/comments/7njz2m/eli5_whats_the_difference_between_degrees_minutes/

For one address it shows two formats, one is latitude, and another one is longitude. Personally, Latitude and longitude could accurately express the location of a place on the earth. Latitude it is the North/South value of a point on Earth, and longitude it is the West/ East value of a point on Earth. Longitudes are lines going from south pole to north pole. 

2) Find the latitude and longitude expressed in both notation systems for four locations of your choosing. One should be north of the equator and east of the Prime Meridian, one north of the equator and west of the prime meridian, one south and west, one south and east). Zoom in and out in the map and find locations (either randomly or based on your curiosity), anything you find interesting and report that location’s coordinates.

1. North of the equator and east of the Prime Meridian

Coordinates: 40.5, 100.5

Degrees DMS: N40°30’0”, E100°30’0”

This is a place in China, 40.5 is a north latitude and 100.5 is an east longitude.

When I convert it, will shows the North of equator and west of the Prime Meridian, which is

2. Coordinates: 40.5, -100.5

Degrees DMS: N40°30’0”, W100°30’0”

This location is at the United States.

3. South of the equator and east of the Prime Meridian

Coordinates: -40.5, 100.5

Degrees DMS: S40°30’0”, E7100°30’0”

This place is the ocean near the Austrilia.

4. South of the equator and west of the Prime Meridian

Coordinates: -40.5, -100.5

Degrees DMS: S40°30’0”, W100°30’0”

This coordinate located at the ocean near the South America.

Part B: Georeferencing a Location

For this part of the lab, you will learn how to use your phone as a GPS. This presupposes you have a smart phone on a data plan.

NOTE: You should incur no costs getting through this lab. If do not have a smart phone with a data plan or if you would prefer not to use your device to complete this assignment, please contact me via email. You are welcome to complete this lab using an alternative technique.

But if you already have a phone, there is no reason on Earth not to learn how to use it as GPS receiver. And it’s really cool!

STEP ONE: Install GPS app

The first thing you need to do is install a free GPS receiver app. I demonstrated via a screenshot in the last two presentations is GPS Status because it is so simple. It is available for free for both Droid (see instructions below). I’m not an iPhone user, but I’ve test driven My GPS Coordinates (see instructions below). There are many other apps to choose from, and you may already have a GPS app installed on your phone. Some are better than others. Feel free to pick your own. If you’re new to this, use the tools I know because it’ll be easier to help you.

STEP TWO: Mark an object, landmark or location.

Using your phone, mark your current location.

Directions for GPS Status app (Droid): to mark the location, open the GPS app and tap the screen. You have the option to share your location. Send it to yourself by text or email. You also have an option to copy the image (at far right when you tap the screen). This creates a screen shot of the GPS status screen. You can also send this to yourself or observe it later. Or if you just want to write it down, that’s fine to.

In the example screenshot I provide these are in the second to last row, written as Latitude and Longitude. Make a note of how they appear: (39°2.292’N, 77°6.161’W). These are not in DD! To change how these coordinates appear, I can change the setting of the app. To do so, tap the screen, click on the icon at top left (three lines). And then tap Settings. Then tap on “Units & Formatting”, then on “Location Format [DD.DDDDDD°]”. You’ll see a list of possible formats. Make a note of how the coordinates of your location are expressed in the following formats: DD.DDDDDD°, DD°MM.MMM, and DD°MM’SS.S”. To do this change the setting and make a note of both latitude and longitude are expressed by writing down the #s or sharing them with yourself.

Instructions for Apple ios:

To note your location, open the My GPS Coordinates app and observe the lat/long. You have the option to share your location. Send it to yourself by text or email. You can also create a screen shot of the GPS status screen by pushing the power and home buttons on your phone at the same time. You can also send this to yourself or observe it later. Or if you just want to write it down, that’s fine to.

What you want to know is the coordinates of your location (long/lat) in Decimal Degrees (DD).

Deliverable for Part B (responses should be inserted immediately below this list):

1) Note the coordinates of the location you have picked in the formats listed above (below)

Coordinates:

Lat 39.98021+-213 ft

Lon -75.15582+-213 ft

2) Explain what these different notations and formats are (DD.DDDDDD°, DD°MM.MMM, DD°MM’SS.S”). It will be helpful to think of this in terms of decimal degrees vs DMS. If you aren’t clear on the distinction, enter both in a google search (or review the lecture or go here: https://www.maptools.com/tutorials/lat_lon/formats or, for a more detailed look, try Wikipedia: https://en.wikipedia.org/wiki/Geographic_coordinate_conversion). Is the information they contain identical or different for each one?

These two formats can convert each other. 60’’ is equal to 1’, and 60’ is equal to 1degree.

3) Explain what latitude and longitude are. What precisely are you expressing with these numbers for long/lat?

Because the latitude is a positive number so that is north of the equator, and because the longitude is negative means the location is west of Prime Meridian. 

Include your responses in this space.

In the example screenshot I provide the coordinates are written as Latitude and Longitude. Make a note of how they appear: (). These are not in DD (they are default in coordiantes)! To change how these coordinates appear, click on the Settings icon at upper right, then select “Settings” and “Coordinate format”. There, you can change from decimal degrees [DD.DDDDDD°]” to other formats. Make a note of how the coordinates of your location are expressed in the following formats: decimal degrees (DD.DDDDDD°), degrees/minutes (DD°MM.MMM), and degrees/minutes/seconds (DD°MM’SS.S”).

Part C: Converting

Everything in Google Maps and all the ways of formatting the coordinates is based on the World Geodetic Survey of 1984 Datum (WGS84). That means that all of these share a basic coordinate system and an ellipsoid model of the Earth. So these numbers for latitude and longitude are expressed using the same coordinate system.

Sometimes our data come from the past, before the WGS84. So sometimes we need to convert from one coordinate reference systems to another.

Go to the World Coordinate Converter (http://twcc.fr/en/#) and pinpoint the location of the geographic coordinates of one of the areas you examined in lab #2. When you click on your location on the map, in the box on the right you will see something like this:

At right, you are seeing the coordinates of you location in DD based on the WGS84 datum. Note that you can switch from DD to DMS by selecting a different button at the below the coordinates. Below that, you can convert these coordinates into other coordinate systems based on other datums. Try this yourself. For instance, in my example above, I have the location of the zero milestone in WGS84 and have converted it to the North American Datum of 1983 (CSRS).

Using the converter, I can see how these coordinates differ in different coordinate referencing systems. For example, I have pasted in the coordinates that that the World Coordinate Converter initially gave me when I first clicked the map (WGS 84). I’ve then pasted in the coordinates for other coordinate referencing systems.

PART C DELIVERABLE:

Insert your own converted coordinates (you can use your current location from part B) by using the World Coordinate Converter:

GPS (WGS84) (deg): 39.98021, -75.15582+-213 ft

AGD 66: 13.208410386218306, -61.262857999999994

ED 1950: 13.208774337256955, -61.262857999999994

MGI: 13.204258288088605, -61.26694390497006

Are the coordinates the same or different? Explain how and why in a few sentences. What does our lecture about ellipsoids and the shape of the earth have to do with these slight changes?

The coordinates mean the same location, but they express in different formats. Since the asymmetry of the earth causes errors, the error will be different when the regions are different.