User-generated maps in IDA 2

Transcription

1 Interference and Direction Analyzer IDA 2 Technical Note TN105 User-generated maps in IDA 2 IDA 2 and GIS software allow use of aerial photos and users own maps It is often useful to be able to use your own maps, aerial photographs, orthophotos, or satellite images which show your own infrastructures. Narda uses the open source Slippy Map Tile System from OpenStreetMap for displaying maps in the IDA2. This lets you display maps quickly and is supported by many GIS programs. This means that you can use any commercial GIS program, such as Global Mapper, to create maps for the IDA 2. The map material used in the IDA-2 measuring system is made up from many image segments, called tiles. These are based on the Slippy Map Tile System from OpenStreetMap. These tiles are rendered from vector maps on a fast computer or server and stored in a preset file structure on the microsd card of the IDA 2 measuring system. This file structure defines the zoom level or georeference of each image tile as well as its name. When you display a section of a map on the IDA-2 measuring system, it puts the individual tiles together like a mosaic to form a complete map. A large number of tiles are needed depending on the zoom level or size of the map section, so that you can move around on the map freely. To make use of the highest resolution maps possible, you need to define the area within which measurements are to be made when planning measurement operations, and then only load the tiles needed for this area or zoom level onto the microsd card. TN105_IDA_1077_E_User-generated_maps 1 / 8 Subject to change

2 Map data structure on the microsd card The map data (tiles) are recorded using the Slippy Map Tile System from OpenStreetMap. An further basic structure has been added to make it easier to manage the map data in the instrument. This is shown by the red boxes in Figure 1 below. The green boxes indicate the elements of the Slippy Map format, which is described in more detail later in this technical note. microsd Card Base Folder Project / Site Name Map Service Zoom Level X Tile Index Y Tile Index The corresponding copyright information must always be saved along with any maps that are created. Therefor please create a text file containing the copyright as a line of text and save it in the Map Service folder. For example: Figure 1: Folder / file structure on the microsd card J:\ Maps\Tiles\ Beijing_City\Mapnik\Copyright.txt The copyright text is displayed at the right hand edge of the map. Please note the copyright terms and usage policy of your map distributor! Figure 2: Recording copyright information Figure 3: Copyright text shown on right hand edge of map TN105_IDA_1077_E_User-generated_maps 2 / 8 Subject to change

3 The map system in detail To generate map material for the IDA 2 measuring system, a vector based Mercator map is rendered into a raster image and divided up into tiles just like a mosaic. Each image tile has a size of 256 x 256 pixels and is saved in PNG format. Zoom level 0 shows the entire world map on one tile. Increasing the zoom level by one multiplies the number of tiles by four, allowing more details to be seen on the map. You can calculate the number of tiles in each zoom level using the following formula: Number of tiles per zoom level = 2 zoom level zoom level x 2 Zoom level 0 Zoom level 1 Zoom level 2 Figure 4: Zoom level 0 ( OpenStreetMap contributors, CC BY-SA) Figure 5: Increasing the zoom level ( OpenStreetMap contributors, CC BY-SA) Georeference and tile index The image tiles are georeferenced by stating the zoom level and the tile index. The zoom level and X tile index are used as the folder names. The Y tile index corresponds to the image tile file name: [Zoom level] / [X index] / [Y index].png The IDA 2 measuring system uses the value m as a constant for the radius of the earth. More details can be found on the OpenStreetMap website. TN105_IDA_1077_E_User-generated_maps 3 / 8 Subject to change

4 Example: Creating maps for IDA 2 using Global Mapper The instructions given here apply to Version of the Global Mapper GIS program. Loading and processing map material First you must upload the desired map material to your PC. Global Mapper supports also renders vector based formats. Some of the possible options are: You can load data from your hard disk. You can use data taken from databases. You can download maps from servers. You can import aerial photographs which are georeferenced when they are imported. Figure 6: Global Mapper Load map material Figure 7: Global Mapper Create New Point \ Text Feature You can draw more details on the map using the drawing functions, such as Create New Point \ Text Feature. This allows you to draw your own infrastructures on the map. In the example here, we have drawn in four (imaginary) base stations. Figure 8: Global Mapper Drawing your own elements in the map Figure 9: Global Mapper Map with four (imaginary) base stations TN105_IDA_1077_E_User-generated_maps 4 / 8 Subject to change

5 Exporting map material for IDA 2 To be able to use the map material in the IDA 2, you have to export it and save it on the microsd card. To do this, click on the File Export Export Web Format menu command in the Main menu of the Global Mapper program. A dialog window opens. In this window, select the export format OSM (OpenStreetMap) Tiles You can make several export settings in the next dialog window (OSM Tiles Export Options). OSM Options tab: Data Set Name You can enter the map name here. Figure 10: Global Mapper Export Zoom Level Setup You can set the maximum zoom level and the number of smaller zoom levels here to make sure that the quantity of data is not too big for the microsd card. Remember that doubling the zoom level multiplies the number of tiles by four (see The map system in detail on page 3). Tile Image File Format You must select PNG here. Transparency and other options The other settings on the OSM Options tab have to do with the display. You should remember that the tiles are not transparent when displayed on the IDA 2. The following settings are recommended: Transparency Opaque Save Vector Data if Displayed ADVANCED: Fill to Tile Bounds ADVANCED: Always Create 8-Bit Palette PNG Files ADVANCED: Export PNG for Transparent Tiles Figure 11: OSM Options export settings TN105_IDA_1077_E_User-generated_maps 5 / 8 Subject to change

6 Export Bounds tab: You can set the section of the map to be exported here. In our example, we have selected the data visible on the screen as the section to be exported. When you click on OK, a new dialog window opens. You can set the location where you want to save the data in this dialog window. The folder structure used on the microsd card is shown on page 2. Figure 12: Export Bounds export settings Figure 13: Save As TN105_IDA_1077_E_User-generated_maps 6 / 8 Subject to change

7 When you plug the microsd card that you have prepared in this way into the IDA 2, you can select the user generated map in the map view (Direction Finding Map). Figure 14: IDA 2 Selecting the map on the IDA 2 This map can then be used in the IDA 2. Figure 15: User generated map displayed by IDA 2 TN105_IDA_1077_E_User-generated_maps 7 / 8 Subject to change

8 Glossary GIS Orthophoto OSM Georeference Tiles Geo-information system. GIS software allows processing and display of geographical data. An orthophoto, orthophotograph or orthoimage (Greek: ὀρθός [orthos] = straight, right, proper) is an aerial photograph geometrically corrected ("orthorectified") such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances, because it is an accurate representation of the Earth's surface, having been adjusted for topographic relief, lens distortion, and camera tilt. [Wikipedia] OpenStreetMap To georeference (also geocode, geotag, localize) means to associate something with locations in physical space. The term is commonly used in the geographic information systems field to describe the process of associating a physical map or raster image of a map with spatial locations. Georeferencing may be applied to any kind of object or structure that can be related to a geographical location, such as specific data, points of interest, roads, places, bridges, or buildings. [Wikipedia] Image tiles from which a complete map can be made up just like a mosaic. More information Mercator projection Wikipedia Slippy map tile names OpenStreetMap Wiki Copyright information: The map sections used as examples from figure 7 onwards are from TNRIS, Texas Natural Resources Information System, part of the Texas Water Development Board. Narda Safety Test Solutions GmbH Sandwiesenstrasse Pfullingen, Germany Phone: Fax: info.narda-de@l-3com.com Narda Safety Test Solutions 435 Moreland Road Hauppauge, NY 11788, USA Phone: Fax: NardaSTS@L-3COM.com Narda Safety Test Solutions Srl Via Leonardo da Vinci, 21/ Segrate (Milano) - Italy Phone: Fax: nardait.support@l-3com.com Narda Safety Test Solutions GmbH The name and logo are registered trademarks of Narda Safety Test Solutions GmbH and L-3 Communications Holdings, Inc. Trade names are the trademarks of their respective owners. TN105_IDA_1077_E_User-generated_maps 8 / 8 Subject to change