Keep coordinates, scale and units straight
See this course’s project requirements
Compare an existing and proposed service location in the supplied fictional four-zone town.
Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.
What to include
- Define the decision and geographic layers with aggregate data.
- Plot a labeled coordinate grid and check units.
- Join attributes by zone ID and document missing-data checks.
- Calculate baseline and closure routes from the given network.
- Compare unique coverage and deliver a map, table and scoped memo.
Review and revise
Use these criteria to check your work and choose what to improve.
- Geographic meaning: layers, units and assumptions are explicit.
- Data quality: IDs and populations match without invented values.
- Calculation: route and unique coverage arithmetic is reproducible.
- Communication: the map supports a limited, accessible decision explanation.
Want more background?
The idea in everyday life
Two numbers do not describe a usable location until their meaning is known. Latitude and longitude use angular coordinates, while many local map systems use distance units. Mixing them can make points or distances misleading. Your exercise uses a simple Cartesian grid in kilometers, so it requires no GPS device, geocoding service or map-account registration.
Coordinates only make sense with their reference system and units.
One step at a time.
Use the sample or information you have permission to use. Keep your work as you go. You can pause between steps.
- 1
Plot the four supplied points on squared paper: A=(0,0), B=(2,0), C=(2,2), D=(0,2). Label the first coordinate eastward x and the second northward y.
- 2
Label the grid as fictional Cartesian coordinates in kilometers, not latitude and longitude. Include a scale note saying one grid unit equals one kilometer in this toy model.
- 3
Measure the direct A-B and B-C separations as two kilometers each. Do not label that distance as travel time; the road layer supplies its own minute values in the route lesson.
- 4
Inspect a planted entry D=(0,2000). It conflicts with the declared kilometer units if its source intended meters. Flag the unit mismatch rather than dragging the point into a convenient position.
- 5
Write what the coordinates mean, which axis comes first, and the units. In real geographic information system (GIS) work, check the coordinate reference system (CRS) and convert coordinates as needed; changing a label alone does not convert them.
See how it works.
Fictional grid: A lies at the lower left, B two kilometers east, C two kilometers north of B and D two kilometers west of C. The town forms a two-kilometer square on the exercise grid. If a file stores D as (0,2000) meters, it describes the same intended offset only after a correct unit conversion to (0,2) kilometers. Merely calling 2000 "kilometers" would place it far away. This example illustrates metadata and conversion, not a real map projection. The final drawing should retain the fictional-grid label so readers cannot mistake it for a geographic survey.
Did you cover these?
- All four points match the supplied grid.
- Axis directions and kilometer units are labeled.
- The meter/kilometer mismatch is flagged.
What to finish
A labeled grid and coordinate/unit quality note.
Watch for this
Measuring a route in degrees or relabeling coordinates without transforming them.
How can I tell I understand it?
Explain why numbers, axis order and units must travel together.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Pass the check. We’ll save the progress.
Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
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Sources and further reading
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Source & access notes · checked 2026-09-10
Opened official CRS and projection tutorial. The exercise uses a labeled fictional Cartesian grid and never presents it as geographic coordinates.
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