Development of a Tool for GIS Map Preparation Using Hand Held GPS Data

: Use of map based information systems is becoming a common requirement for many uses. It is important for comparison of locations, identification of distance, establishment of networks, selection of routes etc. With the hand held GPS equipment becoming more affordable and reasonably accurate, the positions thus obtained require to be taken in to databases for meaningful and comparative applications. GIS software of present day are complex and require incorporation of suitable settings to prepare representative maps. This requires a reasonable knowledge of GIS and GIS software to develop spatial data layers from externally captured coordinates. In an environment where GIS resource persons are scarce, it is necessary to identify methods to overcome this problem of preparing GIS maps using GPS based field data as and when the field data from GPS are made available. Tool was developed using Visual Basic 6 programming language and ArcGIS. Once the captured coordinate are entered and appropriate topo sheet is selected, the ArcGIS software would upload a scanned image of the 1:50,000 topo sheet so that a user could identify and carryout associated computations or management activities, enables a non GIS expert to capture field data with a hand held GPS and support the creation of GIS maps in a very fast and accurate manner. This paper describes the tool planning, design and development which was carried out in a systematic manner. The tool which is provided as an independent software would load the ArcGIS software upon selection and then proceed with the interface operation that enables the field GIS data input through a computer terminal.


Introduction
Recently GPS and especially handheld GPS units have become affordable and hence popular among many people who desire to locate either themselves or their interests in relation to a global reference. A location thus identified requires to be plotted in a map to identify the geographic details related to that location. As such, it is important to have georeferenced maps in a GIS framework so that coordinates identified from the GPS could be plotted to scale. The GIS maps can be either based on scanned images, digitized drawings, satellite images or aerial photography. The handheld GPS data are known to possess a significant error ranging from 3 m to 15 m [1]. Therefore, it is important for a user to be aware of the accuracy when attempting to use such data. Most handheld GPS data are often used for location identification instead of map making. Once a person knows an approximate location then with reference to the other features given on a reliable map, the positioning accuracy could be improved. GIS software such as ArcGIS enables the plotting of a GPS coordinate on a map and then to present the plotted location with reference to a base map. The map could be either a topo map or a satellite image.
In case a person who requires to plot handheld GPS data to a ArcGIS map, it is necessary to have a training on the use of the ArcGIS software to enter and save data sets as GIS layers.
Though this appears as practicable in case of small-scale operations of field data collection, in a situation where a significant number of handheld GPS units are recording field data at many diverse locations, and there is a requirement to produce a number of maps at different places, the preparation of maps with the help of trained GIS software users dose not appear practical. This is more so in a country like Sri Lanka where there are limited GIS resource persons and also where there are inadequate of training opportunities. Under these circumstances the decision makers or planners who require GIS map data, need to find alternatives to achieve their objective of carrying out GIS map preparation to the desired accuracy. A solution to this problem is to develop a simple user interface (UI), which would enable the entry of GPS data, activate a GIS platform, and then plot on a geographic layer to be compared with an acceptable map. Therefore it is very important and useful to develop a tool of this nature to produce maps with handheld GPS data but without the need of GIS software knowledge. This tool needs to be so designed that a user would be required to only be trained in GPS data capture and the entering of captured data in a simple to use Graphic Interface linked with the tool. The interface needs to ascertain reliability of data without leaving room for the occurrence of operator-errors such as mismanipulation of layers or editing errors. With a suitably designed tool users would only require ensuring the accuracy of data entry to develop an accurate GIS dataset. In the present work, development of a tool for GIS map preparation using handheld GPS data is described. The planning, designing, development and accuracy checking is presented in a step-by-step manner. The tool development using Visual Basic 6 activates and carries out map preparation on a ArcGIS platform.

Objective
The objective of the work is to develop and test a tool which enables a non GIS expert to prepare a GIS map incorporating externally collected location coordinates.

General
The methodology used for the study is shown by the process Flowchart in Figure 1. Since the tool need to be used by non GIS experts, the design looked at the options available for the tool to work as an extension. An extensive literature survey did not reveal the availability of a tool which would function as an extension, load ArcGIS, input external data, create a shape file and at the same time write input data written to a spread sheet of a different platform. Therefore efforts were taken to carryout external operations [2] [3], communicating data form ArcGIS to a VBA and vice versa [2] [3], exporting information to a spread sheet [4] [5] [6] etc., through a tool which would initiate action independent of ArcGIS.

Requirement Analysis
A user need assessment was carried out and using a simple questionnaire to capture the needs of the tool [7]. A self-identified 20 GPS, GIS users were taken as the sample to assess the requirements. Questionnaire attempted to identify the type of GPS data recording personnel, adequacy of GPS software available for map preparation on GIS platforms, capability GPS users for map preparation in ArcGIS, and type of a tool desirable to prepare maps using GPS data. Survey questionnaire revealed that an 80% of respondents requested an independent tool for a Graphical User Interface (GUI) to carryout the task in ArcGIS. 30% of the participants requested the capability to view the captured points on a GIS map layer. 40% of the surveyed indicated that the support should be extended to view the GPS captured points not only on a map layer but also on a background map which is either the 1:50,000 topo sheet or a satellite image.

Development of Tool G2G
The process flow of the tool is shown in the Figure 2. The tool, which is to enable plotting GPS data on to a GIS was named G2G.

Figure 3 -G2G Map Recorder GUI
The G2G tool initially uses MS Visual Basic Language Version 6 to modify ArcGIS registry to initiate G2G module action within the ArcGIS environment. At initiation, a data input form to commence either a new recording or to carry out editing of previous data is placed as the active window. New data entering mode highlights a form called the G2G Map Recorder to complete the task up to adding a shape file whereas adding new points by editing an existing dataset could be completed with the second input form named G2G Editor. The two forms are shown in Figure 3 and Figure 4.
The forms were designed as component container using VB6. Order of components in each form shown in Figure 3, Figure 4 was  The G2G Map Recorder GUI functionalities and G2G Editor Functionalities are shown in Table 1 and Table 2. The GUI development incorporated input masking to ensure that only numerical data could be entered for field data input columns. Coding was done to detect an erroneous map selection at the end of each data entry. In order to ensure speedy operations with a shape file, the coding adopted a stepwise initiation of processing during form completion.

Tool testing
Tool testing was carried out in three stages. Initial internal evaluations were carried out to test the flow, process and accuracy of computations [8]. Accuracy to testing of the tool included the checks on validity range for inputs, compatibility with the topographic survey sheet, numeric or text nature of input and the number of possible digits per coordinate. Mapping accuracy of input coordinates was checked by extracting coordinates of plotted point to the layer attribute Table. Once evaluations of the software satisfied internal accuracy testing, user requirements were tested with a self selected sample of known GIS users who were aware of the objective of the tool development and who were both conversant in ArcGIS and GPS. The third evaluation as shown in Figure 1 was conducted with a set of 20 clustered users. Results of the clustered evaluation [10] was carried out to capture user satisfaction with respect to overall software quality. The degree of perceived usefulness and perceived ease of use were assessed with the elements indicated in the Davis approach [7]. Identification of the degree of user productivity revealed that the installation steps to be followed were often skipped and as a result the users were unable to proceed further thereby showing poor results. As a result, the coding was further developed to modify the registry file and BAT file ensuring automatic activation of ArcGIS and tool simultaneously. From the series of success measures cited in literature, user survey incorporated several questions to assess the degree of (i) user understanding of interaction with the system, (ii) Ease of which choices can be made, (iii) Skilled application of system (iv) improvement in choice performance, and (v) Improvement of the ease with which choice can be made.
Once the accuracy of input and plotting coordinates were ascertained, evaluations were made with regards to the relative positioning of coordinates on a georeferenced topographic map sheet or a satellite imagery. Trial GPS coordinates picked from known locations around Colombo were plotted to identify the variation of plotted point and the map location.
Tool testing was carried out by attempting to plot coordinates pertaining to locations identified on hard copy maps. Nine points with one each from a single topographic survey sheet of 1:50,000 was identified and the tool was used to enter the data for a comparison with GIS out puts. Thereafter field GPS points were plotted and checked for accuracy.

Results and Discussions
1. Tool evaluation was carried out though a user survey with a 20 person clustered sample. The questions used for evaluation, results of scores given to each question, frequency of responses are shown in Table  6-1 to 6-6. Results were very satisfactory with a clear indication of the tool achieving the development of objectives.

A sample of map produced by the tool on
ArcGIS platform is shown in Figure 5.
Coordinates of nine points selected from 1: 50, 000 hard copies were fed to the tool and were compared at different zoom levels. At 1: 50,000 scale, no error could be observed in any of the points. However upon zooming at different scales it was noted that there was a disparity. The differences observed on screen are shown in Figure 6. The hard copy identified points were the grid crossing on the 1: 50,000 topographic map. Therefore, it was easier to capture the mismatches on screen. ARCGIS coordinates of map grid points were obtained and comparisons were carried out with the input values. The errors in the input and on screen outputs are shown in Table 3. The errors changed