Research on Key Technology of Land and Resources of Mobile Geographic Information Platform

Studies in Surveying and Mapping Science (SSMS) Volume 3, 2015

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Research on Key Technology of Land and Resources of Mobile Geographic Information Platform YongHua Chen Information and Engineering College, Zhengzhou University, No.100 of Science Road, Zhengzhou, Henan,P.R.CHINA ieyhchen@zzu.edu.cn Abstract For the reason of the office desktop environment restriction, some difficulties in business information acquisition exist in ministry of land and resources’ departments, which lead to great inconvenience for the land survey work, law enforcement and supervision, planning and design, project argumentation etc. The paper completed the design and realization on the land and resources’ mobile geographic information system, which includes business functions of land and location query, outdoor verification, comparison of the maps, data editing etc, by the research on important algorithms and key technologies of the design attribute query based on mobile offline database tile technology and the design of the system structure’s whole frame and so on. The system is an important tool for land management of mobile GIS application, and it is suitable to the land and resources cadastral, law enforcement and planning of various business fields.

Keywords Mobile GIS; Android; Offline Database

Introduction At present, land and resource’s traditional business systems are based on indoor office environment．It is unable for them to obtain relevant business information away from the desktop office environment with computer [1-3].

The paper completed the design and realization on land resources mobile office system based on the Android system. By putting data into the tablet computer or large screen phones and other mobile electronic devices, office staff can search information, process business and make decisions at anytime and anywhere. Land resources mobile geographic information system converts the traditional database achievements into encrypted offline package with slicing technique, so that it can be easily loaded into the tablet computer[4]. The thematic databases include satellite imagery data, two tone data, Town Cadastral data, land use planning data to achieve integration, query and analysis of various types of thematic data and handle official business processes on a unified platform.

System General Design The system through slicing offline mobile database achieves various functions of Land Resources’ mobile geographic information on a mobile platform. The total system frame is divided into three layers: environment support layer, data support layer, and functional view layer, as shown in Fig. 1.

Environment support layer comprises basic platform of Android, ArcGIS for Android environment [5]. The basic platform of Android is the foundation of system operation, it provides the basic Android program running package. The ArcGIS for Android environment provides mobile processing environment, processing mobile environment under GIS platform and provides reading and writing including spatial properties data [6-7], spatial data query positioning operations package; SpatialLite provides the storage management of vector diagram database [8-9] for implementing data management of vector spatial database, attribute database.

Data support layer includes spatial database, business database and business logic [10-12]. This layer, the data

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support layer, provides spatial data and attribute data. In addition to providing the basic data layer outside, this layer also achieves the relevance of spatial data and business data through business logic query.

The functional view layer includes attribute search function, maps contrast function, maps edit and modify function, GPS positioning function and field verification function. Functional view layer provides the basic functions of the system, including basic operation, editing and modifying, attributes querying, maps contrasting, GPS positioning, field verification and other operations. Functional view layer is faced with the operator, who can achieve operation of specific functions through interaction with the Tablet PC. Outwork Verification

GPS Location

Attribute Query

Maps Contrast

Spatial Dtatabase

ArcGIS for Android

Basic Operation

Editing & Modification

Business Database

Business Logic

Android Platform

SpatialLite

FIG. 1 SYSTEM GENERAL DESIGN

System Functional Design Common Functional Design The design of GIS common functions based on mobile platform, is completed according to the characteristics of the moving plate and based on the traditional GIS functions. Common functions include the following specific areas: 1) Map zooming and panning function By clicking the zooming and panning button, the map can be zoomed or panned. The zooming button is put on the fixed position of the main interface while designing the system. The operator can open any map in any state to zoom or pan maps. Because the system is completely based on the Tablet PC operation, the operator can use fingers to zoom or pan maps by dragging. It is easy to operate.

2) Layer Management function When the project is opened, it will generally load multiple layers project. Operators can manage the layer visually or load the layer dynamically according to the demand.

Thematic Functional Design Land resources mobile platform is built on the Android platform to perform related official business of various business offices of the land department. System design, proceed from specific business applications, combined with features of field operations and field positioning of mobile tablet computer, has achieved the following special function of land resources data: 1) Browsing, querying and retrieving of maps’ image information Load the cadastre, planning, land use and other offices of the business maps into the mobile tablet computer by slice, so that you can achieve operations of information browsing, attribute querying in the Tablet computer.

The specific functions are as follows:

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Studies in Surveying and Mapping Science (SSMS) Volume 3, 2015

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The system provides operations which include layer management, zooming and roaming for maps such as earth mapping spot (two tone), cadastre, parcel and other thematic maps and satellite images.

The system provides an index range query for query and retrieval of information of various kinds of spatial maps and business attributes. Under the open project layer (view), you can retrieve the scope of map fast through the index list by place name or region. It is convenient for location query.

2) Comparative analysis of all types of maps, different periods of maps and changing ground objects.

Because land resource data is dynamic, maps comparing is the common function of land resource business. The system provides a comparison based on various kinds of maps, including: Establish synchronized movement zoom comparative analysis of earth mapping spot, cadastre, information of attributes and satellite images by sub-window.

Establish comparative analysis of changes of images’ land use in different periods to carry out the contrast of image map and vector image, the contrast of status map and historical map, the contrast of status map and altered graphs(increment graph).

3) Land parcel boundary of field verifying drawing and editing, the scene forensics data entry Locate and verify the target land parcel and map spot and draw the land parcel boundary while the field and map spot does not match.

Edit the verification information, on-site field photographs, recording, video and forensics of entry drawing area.

4) Land survey GPS services The system realized efficient and convenient search function of target block by entering coordinates or designated plots.

By setting the plot and map spot targets, we can establish a line of GPS positioning navigation to instruct workers to do field search. Moving the Tablet computer's built-in GPS to realize function of field positioning and navigation.

Mobile Offline Database’s Establishment and Information Retrieval Selection of Mobile Offline Database Generally speaking, mobile platform database schema includes two categories: online mode and offline mode. The so-called on-line mode is that releasing map service by the server side. The mobile client completes the whole operation by accessing the server side’s service. The whole system architecture is based on the 3G or 4G communication network architecture. While the offline mode is that the map is on the client and no map services from the server and completing GIS operations and analysis of thematic maps in the mobile client.

From the system performance considerations, offline map mode is better than online map mode. Because the offline mode does not rely on the network, and the map’s accessing and browsing are based on local mode. But the online map mode is based on the communication network structure, and its performance is influenced by the network. Its map’s accessing is based on the network mobile communication infrastructure.

The Technology Status of Mobile Offline Database The produce of mobile offline database technology has solved the drawbacks of mobile online mode because of its high efficiency and its convenient operation of data accessing.

Currently mobile offline database uses two forms: vector data and non-vector data. The offline database using vector data completes accessing and query of data through the built-in services. While the tile data using nonvector data slicing processes the vector data according to the setting scale by tiling technology. The mobile

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platform completes browsing of maps and query of attribute by slice data.

Mobile offline database is usually installed in the mobile device. When we use vector data, because of its poor data confidentiality and easily lead to leakage of data, it will let the unauthorized users get the full vector maps. While the tile data uses form of non-vector maps, although the other non-authorized users access the non-vector tile data, they are unable to get maps’ coordinates, property and other important information resources, which ensures data security.

There is a big difference in maps of offline vector data and tile data in maps’ browsing and attribute’s inquiry, through test, maps based on form of tile have obvious advantage to vector data maps in maps of browsing and attribute’s retrieval.

Processing Flow of The Tile Data System loading all kinds of maps is based on tile of non-vector data. The system’s tile technology is completed through ArcGIS Server platform. This section briefly describes the specific processing flow of system.

Step 1: Prepare MXD file, and edit the vector data into MXD files in ArcGIS; Step 2: Build new service in ArcGIS Manager: enter the file storage directory, generate the file directory; Step 3: Enter the tile parameters, including scale, coordinates generated image formats and other parameters; Step 4: After entering the full parameters, publish services, start system processing of tiles of data; Step 5: Through the system processing, generate non-vector image data according to the setting scale.

Design and Implementation of Maps Attribute Retrieval Under Tile Pattern

Users click on maps

System get the coordinates of clicking

Query the location of vector maps corresponded in SpatiaLite

N

Attribute Query failed

Y Query the attribute information in SpatiaLite

Return the attribute information to system

Prompt no maps attribute information

FIG. 2 PROCESSING FLOW OF DESIGN AND IMPLEMENTATION OF MAPS ATTRIBUTE RETRIEVAL UNDER TILE PATTERN

Achieving attribute information query in tile mode is a key technology. Information of maps under tile mode does not contain any coordinate information and attribute information. The system realizes tile maps attribute

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information and spatial database corresponding maps one to one correspondence by SpatialLite. Specific processes are shown in Fig. 2.

Step 1: Operators click on maps (tile format); Step 2: System obtains coordinate value of click; Step 3: Through coordinate index, query the corresponding spatial database attribute information in SpatialLite; Step 4: According to the coordinates of the index value, inquire attribute values of corresponding object in SpatialLite; Step 5: The system returns attribute values to the front to complete this operation of attribute queries.

If Step 3 is executed, but the query result is that there is no such record value in SpatialLite, then the system prompt there is no such maps attribute information.

Design and Implementation of Mobile GIS function of Land Resources Various types of functional specific operation processes under land resources mobile platform are as follows: 1) Operator first logging on to complete the operator’s identity authentication; 2) After verifying the identity of the operator, it is required to select the offline data packets to finish loading maps; 3) After loading the maps, the operator according the purpose of operation to select function, such as information query of maps, maps contrast, target location etc; 4) During the operation, the system will be accessed and the mobile database will be updated.

Fig. 3 is the sequence diagram of all types of functional design under mobile platform. System objects include User (user), Authentication (authorization verification system), MainForm (main interface of system), MapLoadSystem (maps loading system), MapShowSystem (maps display system), Function (system function), Mobile DataBase (mobile database).

user

Authentication

MainForm

MapLoadSystem

MapShowSystem

Function

Mobile DataBase

Login return status SystemStart return StartStatus

Seledt Map

return status Load Map

return status SelectFun visitDb

return FunOperatStatus

return RecordSets

FIG.3. SEQUENCE DIAGRAM OF ALL TYPES OF FUNCTIONAL DESIGN UNDER MOBILE PLATFORM

User objects send user logon operating procedure Login () to the authorized verification system; Login () completes

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the user's passwords and permissions verification, Authentication is used for handling user’s information verifying operation; after User login, execute SystemStart () method to call System Master interface MainForm, MapLoadSystem object is used to achieve operation of loading maps, MainForm is used to achieve operation of selecting maps by calling SelectMap (); MapLoadSystem is used to achieve operation of displaying and loading maps by calling MapShowSystem. After loading and showing maps, User realizes the selection function by choosing Function, Function required to achieve operations of accessing database and so on by Mobile DataBase objects (mobile database) in the realization of specific functions.

System thematic function completes common GIS function, such as comparative analysis of various types of maps, maps editing and other operations. The core is implemented by the map base class. Now we use maps contrast as an example to describe the specific implementation process. private class MapBased{ // This class defines the basic operation of tablet map class, all operations inherit from this class String MapName,MapDir; // Define the map’s name and storage path String MapType; // Map’s category, 0- vector; 1- image maps float scale_Mix, scale_Max; // Minimum, maximum display scale private SetView();//Set the map’s display view } public class ComparMap { MapBased oldMap,newMap; // Define two contrasting maps object private InitMap(){ // Initialization of two maps object oldMap= MapBased.MapBased(); newMap= MapBased.MapBased(); } private MoveNewMap(){ // Synchronous movement of two objects oldMap and newMap } } Any functional operation can achieve the basic functions’ operation of maps on the basis of definition and encapsulation of the maps objects.

The System Test and Application Effect Performance comparison test and analysis of maps’ offline mode and online mode under the system platform.

Test scheme: test tool of choice is Emmagee platform, Emmagee platform can test the tablet CPU, memory and performance testing of flow resources. Test Method is that test GIS common functions and special functions under

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the platform separately using maps offline mode and online mode, namely testing and analyzing the system response time and resource consumption in two modes and other aspects.

Test Environment: a) Mobile Device Environment: Lenovo IdeaTab S2110A tablet, Android 4.2. b) Online Network Environment: China Mobile 3G mode, the communication signal is good. c) Size of the Sample Maps: Zhengzhou downtown, about 1,000 square kilometers.

1) Test and comparison of maps’ loading response time a) Offline mode: The time from the select to fully display of maps is 2 seconds b) Online mode: Loading and displaying time of maps through 3G accessing servers is 4-5 seconds.

2) Basic operation GIS test of maps a) Offline Mode: The operation is relatively smooth while zooming and panning select maps, the general response time is less than one second; b) Online mode: There will be a response in 3-4 seconds to refresh during the operation of zooming and panning maps.

3) Comparison operation GIS test of maps a) Offline Mode: When you select an image map and vector diagram for Comparison of mobile synchronization, the response time is less than one second. b) Online mode: When you select an image map and vector diagram for Comparison of mobile synchronization, the response time is 2-3 seconds.

Tests show that the mobile platform using the offline mode rather than the online mode has obvious advantages of response time of the system in the aspect of loading maps, basic GIS operations and special functions.

The System Implementation effect

FIG. 4 RUNNING EFFECT OF ATTRIBUTE INFORMATION QUERYING OF MAPS

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Fig. 4 shows the running effect of attribute information querying of maps. Attribute query function is queried and retrieved by all kinds of maps’ spatial information and business attribute information. The system provides an index range query; you can quickly retrieve out the map range according to land name or regions through the index list on the basis of opening project layer. It is convenient for location and query.

Conclusions This paper makes a deep analysis in the related key technology of land and resources of mobile geographic information platform, discusses design and implementation on the system function, model selection and construction routes of mobile database, attribute data retrieval and so on. Land and resources of mobile office system can be applied to business areas such as land cadastre, law enforcement, land use, planning and so on. This system can perfect and replenish the traditional desktop office system, play an irreplaceable role that the desktop office system can not be replaced, change the work mode of locale map, chi, instrument, hand-work that field has before. This system can be able to comprehensively improve office efficiency, making the management of land and resources more effective, scientific in all aspects. Moreover, it also has a great significance to improve the application level of land and resources information system.

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YongHua Chen Male, Henan, China, doctor, an associate professor, Zhengzhou University, information and engineering college , specializes in the research of computer graphics, geographical information system.

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