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IAPRS & SIS, Vol.34, Part 7, "Resource and Environmental Monitoring", Hyderabad, India,2002 
  
hs PA 
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Rainfed 
, Light soils 
HE 
Rice in Rabi & + 
Kharif 
Figure 13. Part of an IRS Image (left; 18 Jan'00) and the Map 
of 14 Cover Types (right), draped over a DEM. 
  
Comparing the NDVI profiles with the crop calendar data 
(IMSD 1995, Kameshwara Rao 1995) shows a good spatial 
identification of all 4 out of the 5 dominant crop calendars 
followed (sugarcane is grown at a limited scale in the rice area). 
jun ju! aug sep oct nov dec jan feb mar apr may 
Kharif (monsoon) Rabi Summer 
* Rice (dominant) 
   
     
Irrigated 
  
  
  
Rainfed; light soil 
  
Cotton 
A 
Y 
  
Sorghum 
Y 
or Safflower 
or Bengal Gram 
or Groundnut 
—— — a! 
Figure 14. Crop Calendars of Nizamabad in Colors that 
Match those in Figures 12 and 13. 
Rainfed; heavy soil 
9. SURVEYING USING MOBILE GIS TECHNIQUES 
Research on professional options to use in the field digital maps 
and to digitize by GPS points, lines and polygons, led to a 
relatively cheap but excellent solution (Figure 15). 
   
  
  
e eo ali M di 
W.B t8 9.0. Armpad 
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Figure 15. The Mobile-GIS Equipment. 
The Compaq-iPAQ pocket PC running at 200 Mhz under MS- 
Windows-CE v.3.09) is able to run Arc-Pad (v.6.0) and to 
connect to a GPS. The Pocket PC has backlight-features so that 
in bright sun the screen is still perfectly readable. 
If proper software settings are adhered to, Arc-Pad is able to 
convert GPS readings ‘on-the-fly’ to the coordinate system in 
use. Any image, GT-Sheet, or shapefile can be displayed in 
Arc-Pad (on the Pocket-PC) ‘as is’. The GPS position is shown 
on the loaded maps or images. The user can save the GPS- 
tracklog (as points in lat-long), or use the GPS to prepare 
shapefiles (point, line, or polygon features in the projection 
system of loaded maps). The software also allows to prepare 
forms (questionnaires), and to draw points, lines, or polygons 
directly by hand on the screen. The *iPaq-Arc-Pad-GPS" 
combination comprises a compact but complete set-up of digital 
survey equipment that can be employed in the field by car or on 
foot. The set-up is tested in a series of countries. 
Raster images are converted into MrSID files using Erdas v5.0 
or Arc-GIS; this reduces image sizes by a factor 20 with hardly 
visible quality loss. Arc-Pad software comes with extensions 
that load into Arc-View or Arc-GIS. 
Most problems with the system relate to knowledge on 
projection systems, to the need to prepare *.prj files containing 
projection information, and to proper use of datum settings. 
Once the GPS is connected, the position accuracy on loaded 
maps will be within 10m pending on a proper GPS reception. 
The next three examples show the gain achieved when using 
mobile-GIS in the field. Besides gains, also avoidance of 
identification errors of locations when in the field is achieved. 
Figure 16 shows that roads and field boundaries can be 
perfectly captured by car or on foot into shapefiles. The Aster 
image, topo-sheet, and digitized features all match properly. 
Analysis done to prepare Figure 6 is based on plot boundaries 
captured by GPS during the survey. Figure 17 shows that 
missing features (roads) on outdated topo-sheets and which also 
show no contrast with its environment (rocks) on a 15m 
resolution Aster image can be perfectly captured while traveling 
around, even in mountainous areas. Figure 18 shows that in 
agricultural areas, when using outdated imagery (6m IRS-Pan 
enhanced), sampled plots can still be perfectly mapped.