OR/15/030 Appendix 1

Nicole Archer, Barry Rawlins, Stephen Grebby, Ben Marchant and Bridget Emmett. 2015. Identify the opportunities provided by developments in earth observation and remote sensing for national scale monitoring of soil quality. British Geological Survey Internal Report, OR/15/030.

Published literature search criteria

The Excel spreadsheet of criteria used in the Web of Science search engine to search for published articles related to remote sensing of physical soil properties is summarised in Table 1. The number of ‘hits’ are the published references found by each search. The references found for the Search terms shown as grey rows, were downloaded to Endnote to create a database of 3663 published references. If the search terms provided more than 1000 ‘hits’, this was considered too many ‘hits’ and the search was run again using more defined search criteria

Table 1 Excel spreadsheet showing the number of references found using 43 different search criteria (shown as ‘fields’).

SEARCH ID	Field 1	Field 2	Field 3	Field 4	Hits
1	Soil AND	remote sensing AND	organic carbon		184
2	Soil AND	remote sensing AND	geochemistry		22
3	Soil AND	remote sensing AND	physical OR	bulk density	51594
4	Soil AND	remote sensing AND	bulk density		39
5	Soil AND	remote sensing AND	soil depth		518
6	Soil AND	satellite AND	organic carbon		143
7	Soil AND	satellite AND	geochemistry		6
8	Soil AND	satellite AND	physical OR	bulk density	51594
9	Soil AND	satellite AND	soil depth		418
10	Soil AND	satellite	bulk density		20
11	Soil AND	airborne AND	organic carbon		130
12	Soil AND	airborne AND	geochemistry		53
13	Soil AND	airborne AND	physical OR	bulk density	51594
14	Soil AND	airborne AND	bulk density		10
15	Soil AND	airborne AND	soil depth		158
16	Soil AND	hyperspectral AND	organic carbon		55
17	Soil AND	hyperspectral AND	geochemistry		4
18	Soil AND	hyperspectral AND	physical OR	bulk density	51664
19	Soil AND	hyperspectral AND	bulk density		2
20	Soil AND	hyperspectral AND	soil depth		59
21	Soil AND	LiDAR AND	organic carbon		10
22	Soil AND	LiDAR AND	geochemistry		1
23	Soil AND	LiDAR AND	physical OR	bulk density	51616
24	Soil AND	LiDAR AND	bulk density		3
25	Soil AND	LiDAR AND	soil depth		50
26	Soil AND	Radar AND	organic carbon		26
27	Soil AND	Radar AND	geochemistry		8
28	Soil AND	Radar AND	physical OR	bulk density	51858
29	Soil AND	Radar AND	bulk density		24
30	Soil AND	Radar AND	soil depth		488
31	Soil AND	Thermal AND	organic carbon		539
32	Soil AND	Thermal imagery AND	organic carbon		7
33	Soil AND	Thermal imagery			239
34	Soil AND	Thermal AND	geochemistry		2
35	Soil AND	Thermal AND	physical OR	bulk density	51615
36	Soil AND	Thermal AND	bulk density		1
37	Soil AND	Thermal AND	soil depth		19
38	Soil AND	Microwave	organic carbon		57
39	Soil AND	Microwave	geochemistry		5
40	Soil AND	Microwave	physical OR	bulk density	51804
41	Soil AND	Microwave	bulk density		22
42	Soil AND	Microwave	soil depth		318
43	Soil AND	Unmanned Aerial Vehicle			23
TOTAL HITS USED FOR LITERATURE REVIEW					3663

The Excel spreadsheet showing the number of hits for two Web searches and 1 Blog search is summarised in Table 2. The overall number of references considered to be of relevance was 44.

Table 2 Excel spreadsheet showing the number of hits for two Web searches and one Blog search using different search criteria (shown as ‘fields’).

SEARCH ID	Field 1	Field 2	Field 2	Field 4	Search tool	Hits	Number of pages searched	Number of useful references
1	Remote sensing	soil	physical	properties	Web	2 180 000	10	39
2	Remote sensing	soil	monitoring		Web	4 110 000	10	1
3	Remote sensing	soil	physical	properties	Blog	8910	10	4
TOTAL USEFUL REFERENCES								44