US Interagency Elevation Inventory: Map Services

The US Interagency Elevation Inventory (USIEI) application, updated in February 2021, also has new map services. Today I want to talk a little about the changes to those services. Much of this will mirror the changes I discussed about the inventory download gdb and geopackage. The USIEI application is driven by multiple map services, including ones from NOAA NCEI, USACE e-Hydro, and NOAA OCM. I’m only going to talk about the services from NOAA OCM that encompass the information maintained by the USIEI partnership of agencies, primarily lidar data sets.


The links to data access and metadata had their own fields in the old map services (still up as of this writing, but not updated). They were embedded in html, which didn’t make them very easy to work with programmatically. The new service has all the links in one field in JSON format. That’s not only the data access and metadata links, but a couple other categories too. The links to reports used to be part of the notes field. The links to map services weren’t there are all. JSON is pretty easy to parse in most programming languages and is easy to understand by humans too. Here’s an example of the links field after running through JSONlint to make it pretty.

	"links": [{
		"link": "https:\/\/\/inport\/item\/49733",
		"label": "Digital Coast Metadata",
		"linktype": "Metadata",
		"linktypeid": 2
	}, {
		"link": "https:\/\/\/dataviewer\/#\/lidar\/search\/where:ID=5036",
		"label": "NOAA Digital Coast",
		"linktype": "Data Access",
		"linktypeid": 1
	}, {
		"link": "https:\/\/\/arcgis\/rest\/services\/JALBTCX\/JALBTCX_Acquisition_Status\/FeatureServer",
		"label": "USACE TopoBathy Lidar Service",
		"linktype": "Web Service",
		"linktypeid": 4

This example only had one link of each type, but there could have been multiple as the data might be hosted in multiple places.

Vertical Accuracy

The other major change is the way vertical accuracy is handled. The were two fields used for vertical accuracy originally. One was numeric and gave the root mean square error (RMSE) in centimeters. The other was a text description. The text was often also in terms of RMSE, but not always. We began to have limitations characterizing data sets that might have multiple estimates of the accuracy. For example, a topobathy lidar data set might have a different accuracy for the bathy than for the topo. There was also the case of the lidar vendor’s estimate versus a third-party estimate. To give us more options, we did a similar change and made it a JSON field. An example return might look like this:

{"vertAccuracy":[{"VertDescription":"13.8 cm RMSE","VertRMSE":13.800,"BasisID":0}]}

The VertDescription and the VertRMSE match the fields that were there previously. The BasisID value tells you what the source of the estimate is. A zero means it’s the legacy value that was there before we could keep track of the source. That’s what most of the values are right now, but new entries should have more information and some of the old ones will be fixed. The current table of BasisID meanings is below, but could be expanded in the future.

Basis IDDescription
0Legacy – Origin not recorded
1Government Estimate of Topography Accuracy
2Vendor Estimate of Topography Accuracy
3Third-Party Estimate of Topography Accuracy
4Government Estimate of Bathymetry Accuracy
5Vendor Estimate of Bathymetry Accuracy
6Third-Party Estimate of Bathymetry Accuracy
7Government Estimate of Combined TopoBathy Accuracy
8Vendor Estimate of Combined TopoBathy Accuracy
9Third-Party Estimate of Combined TopoBathy Accuracy
Table of Basis ID meanings for the vertical accuracy field.

New Fields

There are some new fields to hold information that we weren’t capturing before. These are still sparsely filled out and adding the information for the old records will take some time. The fields, such as leafOnOff and ContractSpec were described in the post about changes to the GIS download.

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