Just another WordPress.com site

Map Projection in the 3D Environment

 

Do 3D map applications use projected maps?

Yes.

Why? Why flatten (project) the world if you are just going to use them in a 3D environment; isn’t that a runaround?

Yes, but necessarily.  Raster map images must first exist as a 2D map image.  These map images are then stretched over a sphere in the 3D environment.  The map tiles exists natively as a 2D graphic that is warped over the 3D surface.  Geographic data that is collected, compiled, and served up need to have some base spatial awareness/reference.

What does Local.Live 3D do?

Virtual Earth map tiles are pulled in and draped over a 3D sphere.  Since these map tiles are originally in Mercator projection (not the best projection for draping over a sphere -see the Google Earth image below), they go through a re-project warping process.  A happy result of using Virtual Earth map tiles is that you can switch between the map styles (unlike Google Earth), just like in 2D -which is pretty cool.

 

One quirk of the Mercator projection is that not all of the earth can be included in a single map -it’s just an artifact of the projection, I’ll explain why in a future entry.  The result is no coverage in the polar regions.  So Local.Live 3D must paint-in those polar gaps.  Here is an illustration of where those coverage gaps are:

It’s a good thing for Mercator users that not much is going on around the poles.

What does Google Earth do?

Unlike Local.Live, Google Earth does not use the map tiles you see in maps.Google.com, it streams in aerial imagery from a different source.  Since this imagery is not Mercator (maps.Google.com map tiles are Mercator), this means that Google Earth does not have coverage gaps in the poles.  But it is kind of a bummer because you can’t switch the map style to streets, like you can in 2D.

Google Earth does allow users to pull in outside map images on the fly and pin it to the 3D surface.  In order for map to line up, though, it must have a Platte Carre projection -not Mercator.  Check out the difference between these two overlays.  The one on the left is Platte Carre, the one on the right is Mercator.

What would it take to have a projection-less 3D map application?

It’s so improbable that it blows my mind, but here is what it would take:  That application would have to be comprised entirely of vector data (that means no satellite imagery -which isn’t much fun) and would exist in a holographic state where the geographic data was positioned perfectly upon a perfect model of the earth’s shape (the ultimate datum). Not likely.

John Nelson / IDV Solutions / john.nelson@idvsolutions.com

 

30 responses

  1. Unknown

    adapter laptop

    toshiba 15V 6A 90w 6.3mm*3.0mm adapter PA2501U PA2521U PA3201U-1ACA
    toshiba 15V 8A 120w 6.3mm*3.0mm adapter PA3201U-1ACA SEB100P2-15
    toshiba 15V 8A 120w special 4 hole adapter PA3237U-1ACA PA3237U
    toshiba 19V 3.42A 65w 5.5mm*2.5mm adapter PA3467U-1ACA PA3396U-1ACA
    toshiba 19V 3.16A 60w 5.5mm*2.5mm adapter PA3097U-1ACA
    toshiba 19V 4.74A 90w 5.5mm*2.5mm adapter PA-1750-04

    toshiba 19V 4.74A 90w 6.3mm*3.0mm adapter PA3201U-1ACA SEB100P2-15.0
    toshiba 19V 6.3A 120w 6.3mm*3.0mm adapter PA3290U-1ACA
    toshiba 19V 6.3A 120w 5.5mm*2.5mm adapter PA3290U-2ACA PA-1121-08
    universal 12-20V 90W universal adapter laptop
    universal 12-20V 120W universal adapter laptop
    universal 12-20V 70W universal adapter laptop

    October 13, 2008 at 4:52 am

  2. Unknown

    Hi,Do you have used LCDs, used flat screens and secondhand LCDs? Please go here:www.sstar-hk.com(Southern Stars).We are constantly buying re-usable LCD panels and working for LCD recycling.The re-usable panels go through strictly designed process of categorizing, checking, testing, repairing and refurbishing before they are re-used to make remanufactured LCD displays and TV sets.Due to our recent breakthrough in testing and repairing technology of LCD, we can improve the value for your LCD panels.
    website:www.sstar-hk.com[cecdhjcfbadbhi]

    October 15, 2008 at 11:40 am

  3. Unknown

    婚纱礼服 礼服 聚氨酯直埋保温管 发泡设备 屋顶通风器 屋顶通风器 温泉度假村 雨花石 南京雨花石 雨花石工艺品 五彩石 玛瑙石 彩瓦设备 秸杆门设备 隔墙板设备 磁力仪 探矿仪 探矿仪器 电视墙 操作台 控制台 烟囱维修 烟囱拆除 软连接 编织线 铜带软连接 铝带软连接 母线伸缩节 求购冲压 触头 导电杆 flexible conductors braided copper 数码快印 现场执法记录仪 bullet-proof vests 蛭石 彩砂 石英砂 detox foot pad slimming capsule ginseng royal jelly 呼叫中心系统 电话录音系统 银杏 烘干设备 喷涂设备 无尘设备 防火门 起重搬运 数控旋压机床 泡沫玻璃 超声波探伤仪 波探伤仪 测厚仪 婚纱礼服 礼服 胶原蛋白 隔断 活动隔断 活动屏风

    November 25, 2008 at 2:06 am

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s