GLOBE Data User Guide

The purpose of the GLOBE Data User Guide is to help scientists and researchers understand, access, and use available GLOBE data. The scope includes data collected by GLOBE-trained teachers, students, and citizen scientists as well as data collected from automated weather stations and data loggers.  

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2019-10-09 Latitude and longitude data

Latitude and longitude data #

9 October 2019

Effective September 15, 2019, the site location as defined by the Military Grid Reference System (MGRS) and the true latitude and longitude of an observation made with the NASA GLOBE Observer mobile app are both returned by the GLOBE Advanced Data Access Tool (ADAT),GLOBE Visualization System (Vis), andGLOBE Application Programming Interface (API) in the downloaded dataset. GLOBE Observer data are impacted (i.e., observations made with the Observer app). Need help? Contact help@globe.gov.

Background #

GLOBE uses the Military Grid Reference System (MGRS) as a reference geographic coordinate system. You can read more about the MGRS grid in the GLOBE Data User Guide. If a user queried the GLOBE database, the user would see a latitude, longitude, and elevation associated with each GLOBE observation in the downloaded dataset. For data submitted via the GLOBE Online Data Entry Form, GLOBE Data Entry app, or GLOBE Email Data Entry, the latitude, longitude, and elevation in the downloaded dataset were the location data input by the participant. For data submitted via the GLOBE Observer mobile app, the latitude, longitude, and elevation in the downloaded dataset were defined at the lower left corner of the associated MGRS gridbox and were based upon the first observation submitted from any participant and any protocol that fell within the associated MGRS gridbox.

What changed? #

Effective September 15, 2019, the site location as defined by the MGRS grid and the true latitude and longitude of an observation made with the NASA GLOBE Observer mobile app are both returned by the GLOBE Advanced Data Access Tool (ADAT),GLOBE Visualization System (Vis), andGLOBE Application Programming Interface (API) in the downloaded dataset. Data submitted via the GLOBE Online Data Entry Form, GLOBE Data Entry app, or GLOBE Email Data Entry are not impacted. This change only affects GLOBE Observer data.

Effective September 15, 2019, satellite matching for GLOBE Observer Clouds is now utilizing the true latitude and longitude. Previous GLOBE Observer data was matched coincident to MGRS.

The “true” location of an Observer measurement is the latitude and longitude recorded by the Global Position System (GPS) reading from a person’s mobile device. The GLOBE Observer app does not convey GPS elevation, but instead a Google web service is used that determines elevation based on WGS84 EGM96 geoid height.

Below is an example of the new, updated data output from ADAT . The example is for land cover data. The site latitude, longitude, and latitude associated as defined by the lower left corner of the MGRS grid box are in columns E, F, and G, respectively.

The true GPS latitude, longitude, and elevation of GLOBE Observer measurements are in columns AS, AT, and AU respectively.

Here is an example of land cover data output from the GLOBE API. The variables "latitude", "longitude", "elevation" highlighted yellow are the site location as defined by the lower left corner of the MGRS grid box.

The variables "landcoversMeasurementLatitude", "landcoversMeasurementLongitude", "landcoversMeasurementElevation" are the true location of an Observer measurement.

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