Comparison of WQN site coordinates in the WQI and WQN datasets


Methods

Tim and I noticed some issues with WQN site locations. This was evident at WQN0453: the WQI dataset had this station on Cedar Run in Clinton Co. (trib to Fishing Ck); however the WQN dataset puts WQN0453 on a different Cedar Run in Tioga Co. (trib to Pine Ck).


To determine if this was an isolated case, or if similar issues affected more WQNs, we took the following steps:


  1. We extracted all WQN stations included in the most recent WQI run
  • We then extracted all unique combinations of WQN station, latitude, and longitude from the WQI dataset
  • There were 185 WQN stations included in the latest WQI run
    • There were no duplicates (meaning all WQNs had the same coordinates)


  1. Next, we took a lookup table of WQN locations provided by Molly and merged to the WQI datset (described above)
  • This allowed us to compare the coordinates used for each WQN station in the WQI and WQN datasets


  1. We calculated the difference (absolute value) of latitudes and longitudes used for WQN stations in the two datasets
  • If there was a difference of >0.001 in latitude or longitude, we retained the site
    • The result was 33 WQN stations with a >0.001 difference in lat or long


  1. The 33 sites are shown on the map below

  • Sites with the same WQN number are shown in the same color

    • Site coordinates from the WQI dataset are shown as large circles with hollow centers

    • Site coordinates from the WQN dataset are shown as smaller circles with filled centers


  • If there are no real differences, there should be a ‘bullseye’ appearance, where the small circle lies inside the large circle


  • If there are substantial differences, circles will appear separated
    • You can click on the points to view information to identify issues




The sites with the biggest differences in coordinates between the WQI and WQN datasets are:

  • WQN0453 – Cedar Run (identified previously)

  • WQN0302 – Susquehanna River near Retreat State Prison (~Wilkes Barre)

  • There are minor differences in site locations for the remaining 31 sites

  • Differences are most likely due to snapping sites to NHD while creating sites in SIS

    • To rectify, sites should be modified in SIS

      • This will correct the problem for future WQI runs