GIS Lab 2 HW 3

Author

Brandon Flores

When observing these three outcomes using soley the NAD83 (4269), the NAD83 “South Central Texas” Projection (2278), and the “Texas Centric Albers Equal Area” Projection. The NAD83 solo had its outcome in Meters between the two UTSA campuses which when converted to miles was about 12.15148 miles. For the “South Central Texas” Projection it estimated the two locations at about 12.129 miles. The South Central Texas projection initially had its outcome in US feet. Finally, the “Texas Centric Albers Equal Area” Projection had its outcome in meters as well with a conversion to miles reading about 12.13924.

Although the three outcomes in miles are relatively small in difference there is still a difference. It is very important to have the correct measurements when observing the distance of two locations. Being able to have consistent results is very important.

Call Packages from Library

Read in Bexar county tracts

Getting data from the 2015-2019 5-year ACS

Downloading feature geometry from the Census website.  To cache shapefiles for use in future sessions, set `options(tigris_use_cache = TRUE)`.

Using the ACS Data Profile

Find Coordinate System of Current Map

We see these tracts are in a Geographic Coordinate System (GCS) called North American Datum 1983 (NAD83).

NAD83 Solo

Warning in st_centroid.sf(twtr3): st_centroid assumes attributes are constant
over geometries of x

st_distance(tr_co3)

Units: [m]
         [,1]     [,2]
[1,]     0.00 19555.86
[2,] 19555.86     0.00

19555.86/1609.34 #To get meters into miles

[1] 12.15148

Re-Project Map into “South Central Texas” Projection

Warning in st_centroid.sf(twtr): st_centroid assumes attributes are constant
over geometries of x

Measure Feet Apart

st_distance(tr_co)

Units: [US_survey_foot]
         1        2
1     0.00 64041.12
2 64041.12     0.00

64041.12/5280 #To get feet into miles

[1] 12.129

Re-Project Map into “Texas Centric Albers Equal Area” Projection

Warning in st_centroid.sf(twtr2): st_centroid assumes attributes are constant
over geometries of x

Measure Meters Apart

st_distance(tr_co2)

Units: [m]
         1        2
1     0.00 19536.16
2 19536.16     0.00

19536.16/1609.34 #To get meters into miles

[1] 12.13924