Queries

A user can create a query by issuing a QueryRequest message of the CatalogService to ECHO. Users can search on collections (referred to as a “Discovery Search,” or on granules (referred to as an “Inventory Search”). Table 1. shows the kinds of queries that ECHO supports, with examples of what a collections search might yield.

Table 1: Discovery Search - Collections.

Search Criteria	Search for collections based on
Campaign	Soil Collections,River Discharge (RIVDIS)
Dataset ID	15 MINUTE STREAM FLOW DATA: USGS (FIFE)
ECHO Insert Date	The date it was inserted into ECHO e.g. from July 3, 2001 at 5:30 pm
ECHO Last Update	The date the collection metadata was last updated in ECHO.
Online Collections Only	Only those that are available online
Parameter	Geo-physical parameter
Processing Level	1A, 2B, etc
Sensor Name	BAROMETER, CAMERA, SWIR
Short Name	AST-L1A, MYDPT1KN
Source Name	DIGITAL ELEVATION MODEL, NOAA-9
Spatial	Polygon, polygon with holes, multi polygon
Spatial Keywords	Global, United Kingdom, Solar
Temporal	Search over the temporal coverage of the collection
Temporal Keywords	January, Spring, Stone age, Weekly
PSA Names	DAR-ID, QAFRACTIONGOODQUALITY,FIREPIXELS
Orderable items	Collections available for ordering

In order to build efficient spatial queries we should be aware that:

• If you are querying a single provider, name the provider in the query
• It is best to include the name of the Collection in the query as well
• Smaller spatial regions query faster
• Spatial regions with fewer points query faster
• Spatial queries are well,CPU-intensive