Author: AdminDave

David McSpaden is a GIS Analyst

Projections for Maryland Infrastructure

DRAFT – This is a work in progress

For infrastructure GIS in Maryland, most GIS systems store geometry in the Maryland State Plane NAD83 coordinate system. That standard was adopted in 1987 and required by 1992. (1) However, the average age of a water main in the Baltimore metro area is 70 years and a lot of it is older than that. When you look at those drawings those you will find other coordinate systems. What are they and how do you identify them?

Maryland State Plane NAD83

Let’s start with the current one. It’s commonly called Maryland State Plane NAD83 and the EPSG code is 2248. A large false easting is used to keep all the numbers positive and to distinguish it from NAD27.

Tick on a 2017 drawing in NAD83

  • Minimum X:~600,000 feet
  • Minimum Y:~90,000 feet 
  • Maximum X:~1,900,000 feet 
  • Maximum Y:~800,000 feet 

If your coordinates are outside these values you are out of state or you’ve guessed the wrong system.

Maryland State Plane NAD27

Prior to NAD83 we had NAD27. This system also uses false easting to keep the numbers positive but the range is lower. You should not see these coordinates on drawings dated after 1992.

  • Minimum X: ~80,000 feet
  • Minimum Y:~35,000 feet
  • Maximum X:~1,400,000 feet
  • Maximum Y:~700,000 feet

Baltimore City

Baltimore City and water projects in Baltimore County will have tick marks using Baltimore’s coordinates system. The point of origin is the Washington Monument at North Charles St and Monument St. False easting and northing are not used. Negative numbers are used south and west of the origin and the values are small compared to the state systems. There is no EPSG code for this system. You can download the projection file here.

1936 Drawing with Baltimore Coordinates
2017 Drawing with Baltimore Coordinates

Washington Suburban Sanitary Commission’s (WSSC)

Content Pending

Were you expecting political maps?

Every ten years, the United States redraws the boundaries of congressional districts. The constitutional intent was to maintain equal representation in the house of representatives as the population both grew and moved throughout the country.

However, these maps are drawn by elected officials in charge at the time and they know that moving a boundary can win or lose votes. Drawing a boundary for political advantage is called ‘gerrymandering’. Britannica.com describes it well. Adam Ruins Everything says it all in just two minutes.

The ‘Independent Maps’ movement aims to put redistricting in the hands of non partisan commissions. In theory, they would draw election boundaries that better represent communities instead of carving out districts that favor one political party. You can see your House of Representative’s districts here:

https://www.govtrack.us/congress/members/map

The best way to view these boundary maps is to pick an area you know. Think about the people that live there. Think about their economics, faith, and education. Is the area more conservative or liberal? Then look at the election districts. The lines will either cut through communities to divide their vote or pack a minority party’s voters into fewer districts giving them less representation. This is why your districts are such irregular shapes. Both parties do this.