jtls new terrain generation capability

JTLS New Terrain Generation Capability

Harold YamauchiROLANDS & ASSOCIATES

16th JTLS International Users Conference 4 March 2014

• Current JTLS terrain representation:– Hexagon grid projected upon a 2000 NM by 2000 NM area (terrain board)– Hexagons are typically in the 5 KM – 7.5 KM range (from hex edge to opposite

hex edge)– Terrain is not represented beyond the terrain board– JTLS Model allows placement of naval units, airbases and squadrons off the

terrain board without terrain-related restrictions

• New terrain requirements (J-7):– Represent terrain world-wide– Any type of unit should be able to be placed anywhere in the world and operate

in the same manner as they currently operate on the JTLS terrain board– Implication: Abandon terrain board concept

Background

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• Review three areas of effort:– Define terrain characteristics and features

necessary for a JTLS game– Search for data provider(s) who can provide

the terrain data– Development of a graphical tool for the JTLS

user to access the data, and edit and save portions of it for a specific JTLS scenario

Implementation


• Seven terrain types:1) Air Corridor Network - Paths flown by aircraft while monitored by air traffic control2) Rail Network - Connected network of railroad lines (mainlines only)3) River Network - Connected network of (navigable) rivers used by small boats and

barges4) Road Network - Roads that a ground unit or a convoy should follow5) Shoreline Segments - Represents shoreline locations or divisions between a land

mass and surrounding water6) National Boundary Segments - Represents the borders between two political

entities7) Terrain Grid - A grid representing the underlying terrain

• JTLS already represents the first six in some form (not necessarily as networks)

• Terrain grids are a new element for representing terrain

Terrain Data Types


• A terrain feature represented by a network (air corridor, rail, river or road network) is used by the JTLS model to:– Find an (optimal) path between any two points that can be visited within the

network– Schedule movement for an object following that path

• All networks are comprised of arcs and nodes– A node contains location information in latitude and longitude, and possibly some

additional information such as a name to be viewed by the JTLS user or a delay time (for a rail, river or road node) for scheduling movement through the network.

– An arc connects two nodeso Each arc contains information that the JTLS model uses to find a path through the

network, or uses to affect movement of an object traversing the arc. An example is the representative distance of a rail, river or road arc.

o An arc is considered bi-directional

General Network Representation


• Terrain is represented in levels of detail (LOD). Higher LODs are nested inside lower LODs.

• For each LOD, terrain is represented by grid squares of fixed size. As the LOD increases, the size of the grid decreases.

• Grid squares are equal in size from a latitude and longitude perspective, not a distance perspective. (The JTLS model will properly process the differences of area covered by each grid square.)

• Largest grid size (lowest LOD) is 10 degrees by 10 degrees. Smallest grid size (highest LOD) is 30 seconds by 30 seconds. (See Figure 1)

• Terrain characteristics of the grid affect the JTLS model, such as the ability of sensors to detect objects and ground unit mobility

Terrain Grid ( 1 of 4)



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Figure 1. Terrain Grid RepresentationExamples of grids of size 10 degree x 10 degree, 5 degree x 5 degree, 2 degree x 2 degree, 30 minute x 30 minute and 5 minute x 5 minute.

• Each grid square is assigned a terrain type:– Open– Rolling Hills– Forest– Jungle– Desert– Swamp– Mountain– City– Ocean– Small Island



• Each grid is assigned a road coverage type as follows:– No Roads– Poor Roads– Good Roads

• Other grid attributes:– Max Elevation– Average Elevation– Average Depth



• R&A is currently searching for sources of unclassified terrain data in ESRI shape file format.

• Both commercial vendors and internet sites are being considered.

• Issues:– A single source would be ideal, however no source has all the data

being sought: air corridors from air charts, roads, rivers, railways, national boundaries, shorelines, terrain characteristics and elevation.

– Shape files include a binary .shp file that hold the coordinates of some terrain features and a dBase III .dbf file holding the attributes of the features. There is no standard applied to the structure of the .dbf file. The attributes included in the .dbf file is left to the provider. Many needed attributes such as width, depth and height are not included.

Data Sources (1 of 2)


• For elevation, R&A is using NOAA’s ETOP01 Bedrock Global Relief Model– Elevations are held in 1 minute by 1 minute grids that span from

pole to pole and from -180 degrees to 180 degrees in longitude

• In order for the development of the terrain tool to proceed, R&A is currently using VMAP0 data in shape file format obtained from the GIS Lab website.

Data Sources (2 of 2)


• Objectives:– Provide the JTLS user a method to retain reusable terrain data

in a master database– Provide the JTLS user with a graphical tool to access this master

data, edit and save portions of the data for a specific JTLS scenario

– Export the data in a JTLS scenario format• These capabilities require the addition of a graphical tool

(called the JTLS GIS) for preparing terrain grids, terrain characteristics, national boundaries, shorelines and all of the networks previously listed.

JTLS Terrain Tool Design


• Summary of the process (see Figure 2):Step 1. Shape files that provide the type of data needed for JTLS are added to the master databaseStep 2. Reformat data to master database specificationsStep 3. Data covering the desired scenario theater are selected graphically from the JTLS GIS tool for a new project.Step 4. The terrain features (represented as points, polylines and polygons) are edited as required with the JTLS GIS tool and can be saved back to the project.Step 5. The data can be exported at any time to the associated scenario files. These files are currently to be provided in ASCII text format.

Deriving JTLS Scenario Formatted Files (1 of 2)


Deriving JTLS Scenario Formatted Files (2 of 2)


Figure 2. Steps for Deriving JTLS Scenario Files

External ESRI Shape File Sources(1) Obtain various shape files

Master Shape File DB

(2) Reformat the data and store

JTLS GIS

(3) Select data from Master DB for individual projects

(4) Edit project data

Projects #1#2

#3Scenario Files *.rr*.rr_nnetc.

(5) Export to scenario files

• Real-world data of rail, river and road features are highly detailed polylines containing many (often hundreds but sometimes thousands of) points

• When converted to arcs and nodes, and if left as is, the sheer numbers of arcs and nodes will have a major impact on JTLS memory resources and computational speed

• The solution is to provide the JTLS user with the ability to tradeoff detail (numbers of arcs and nodes) for gains in computational performance by defining a minimum arc length and maximum arc deviation from the real world data

Thinning Networks


Minimum Arc Length


The upper polyline, represented by 16 nodes and 25 arcs, was retrieved from the master database where, for illustration purposes, the nodes are 1-unit apart. If the user chooses a minimum arc length of 3-units, the result is the lower polyline reduced to 6 nodes and 5 arcs. There is no significant change to the original representation but will reduce the computational burden with respect to finding an optimal path.

Figure 3. Minimum Arc Length Example

Maximum Arc Deviation


Figure 4. Maximum Arc Deviation Example

The polyline is abstracted further by the user specifying an acceptable maximum deviation from the original polyline. The resulting polyline has fewer nodes and is within the deviation specified for the scenario.

Maximum acceptable arc deviation

JTLS GIS Screenshots

Questions

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jtls new terrain generation capability

Documents

jtls terrain boardimplication

terrain characteristics

terrain datadevelopment

jtls user

terrain boardjtls model

jtls gamesearch

network air corridor

nm area terrain boardhexagons