Google Earth vs. RG Map vs. GPS Tracks

[arvin555]

I have recently been using the View in Google Earth feature of Mapsource, mainly because I am starting to try out Polygons (Thanks Reijii and Doki).

I know that in one of our FAQs we are warned not to use GE as a one is to one reference against RG map, but I'd like to ask:

1. Using the View in Google Earth Feature, I often find that my tracks exactly follow that of what I see in GE. So the Sat picture vs. my Tracks agree with each other.

BUT, sometimes, like in one road in Tagaytay, I was surprised how "off" my tracks were, and I have used 2 separate tracks on separate dates, and still the GE road did not co-relate with my tracks.

I wonder why this is so? I doubt it is accuracy or lack thereof of the GPS.

Q: I wonder how accurate or inaccurate GE is? Well it is surprising that in some parts it is very accurate, in other parts it is not.

I also imagine that it has to do with the resolution of the sat photo? There are some parts that you can see cars and even persons from the sat photo, while others they don't have details yet. I wonder if GE is not able to accurately adjust the picture vs. GPS position for these?

Q2: Anyone notice that if ever? That in areas where GE has very high resolution photos, that our tracks and Waypoints would jibe? But when you get to areas with less resolution they don't?

2. I also know that the reason why we are asked to contribute 1sec tracks is for continued calibration of the RG roads vs. actual tracks made by RG members. at least this I understand, and probably related to my above question about Google Earth calibrating their photos depending on the resolution of photo available?

TTFN
Arvin

[hbt]

GE not accurate

hmmm... you answer your own question.

maybe i should delete this hehehe

[Reiji]

I have recently been using the View in Google Earth feature of Mapsource, mainly because I am starting to try out Polygons (Thanks Reijii and Doki).

I know that in one of our FAQs we are warned not to use GE as a one is to one reference against RG map, but I'd like to ask:

1. Using the View in Google Earth Feature, I often find that my tracks exactly follow that of what I see in GE. So the Sat picture vs. my Tracks agree with each other.

BUT, sometimes, like in one road in Tagaytay, I was surprised how "off" my tracks were, and I have used 2 separate tracks on separate dates, and still the GE road did not co-relate with my tracks.

I wonder why this is so? I doubt it is accuracy or lack thereof of the GPS.

Q: I wonder how accurate or inaccurate GE is? Well it is surprising that in some parts it is very accurate, in other parts it is not.

I also imagine that it has to do with the resolution of the sat photo? There are some parts that you can see cars and even persons from the sat photo, while others they don't have details yet. I wonder if GE is not able to accurately adjust the picture vs. GPS position for these?

Q2: Anyone notice that if ever? That in areas where GE has very high resolution photos, that our tracks and Waypoints would jibe? But when you get to areas with less resolution they don't?

2. I also know that the reason why we are asked to contribute 1sec tracks is for continued calibration of the RG roads vs. actual tracks made by RG members. at least this I understand, and probably related to my above question about Google Earth calibrating their photos depending on the resolution of photo available?

TTFN
Arvin

if your unit has accuracy of +/-4m or less, its better to rely on it than GE.
GE photos are tiled so you cant get seamless/perfect interface with it.

[arvin555]

Thanks for your reply Guys.

HBT, hehehe, I'm picking everyone's brains, I have my theories but maybe others know more about or can confirm my theories.

Kuya Reiji, thing is if you look at the border between the photos of GE that has a higher resolution and the one with low resolution, there is a slight offset or difference, maybe that can be the cause of some inaccuracies.

At least in my experience using tracks, most of the 1sec tracks I upload in mapsource usually will jibe with Google earth, within metro.

I should go and try some more 1sec tracks around the metro to double check what I just said

With waypoints, I agree it is not 100% accurate because when we save our waypoints, we are not usually right on the spot, if it's a structure, unless if it's a bridge, park and what not.

I guess one reason why I ask this is because we do allow and invite people to use GE to contribute to our RG map. So we need to know how these two maps GE and RG relate to each other

Kuya Reiji, I agree with you about trusting the 1sec tracks more. Then again I should always remember to double check the accuracy during the tracking. I take it there is no way for us to check the accuracy information after we have downloaded the tracks?

TTFN
Arvin

[docsamcruz]

come to this of this, you are tracing ge on a two - dimension or 2d. so the peak & trough of a road wont show much in ge. your gps is tracking the actual length of the road.

the best example of this is an uphill rd, your gps will reflect the actual length of the road but in ge tracing. the uphill road would somehow be lesser in length depending on the angle.

[docsamcruz]

a lot of factors comes into play...first is the ge. if you noticed, the picture like sir reiji explained is made up of picture tiles laced together wherein some parts may not really be interlaced perfectly. one wrong interlacing lead to another to complete the picture.

second is the varying satellite your your unit receive from places to places and time to time not to consider the strength of of the signal. which again is affected by many factors, like weather, clouds, transmitter, etc.

third, the terrain of the road if it is elevated or not. my explanation above will explain this part.

next, the way the ge was traced. followed by the conversion wherein tracks converted are layed out in a pixelized fashion.

etc, etc.

in short, one imperfections lead to another. but better than nothing at all.

[Borgie]

Hi Arvin55. Please check out the imagery dates (see lower left corner of GE screen that appears when you zoom in to see more detail). IMHO, the more current the date, the better the accuracy of GE. In Negros, the most current imageries are dated June 13, 2010. I've checked some of my 1-sec GPS tracks and they are spot on when overlayed on the imageries with 2010 dates but not so with those dated 2004 and 2005...

[arvin555]

Thanks Borgie,

Yes will try checking the date out and will update here. I have two specific locations in GE and one fits with our map as well as my tracks while the other is quite off.

TTFN
Arvin

[arvin555]

Borgie,

You are right, I checked GE date of the area that won't match with my tracks and WP, and they were from 2007. The ones that were from 2009 is way more accurate.

Thanks for this info.

TTFN
Arvin

[Loop]

Just a Qs for this access road, wherein GE have the existing road and its not in our RG Map.This is the access road from ortigas rosario plyover right u turn going to EastBank road in Pasig...http://maps.google.com/maps?f=q&sour...,0.003315&z=18

Can we make use of this GE map as reference to update our RG map too?

[hbt]

google map ---- no
google earth ---- yes

[Borgie]

Just a Qs for this access road, wherein GE have the existing road and its not in our RG Map.This is the access road from ortigas rosario plyover right u turn going to EastBank road in Pasig...http://maps.google.com/maps?f=q&sour...,0.003315&z=18

Can we make use of this GE map as reference to update our RG map too?

Yup use Google Earth not Google Maps as advised by kuya HBT... http://roadguide.ph/forums/showthread.php?t=22

[jnieurzyla]

GE as a source

Could we use GE as the basic source over laid with its roads, as a basis for creating a map for our routes?, of course these would have to be verified by GPS.

I live in an area where there is many new estates and roads, to be honest it would cost me a fortune to travel everyone. at the moment some of these new roads would save my gas, as they are shorter than the GPS maps, and I am reluctant to travel down a new road when I see it on the road, as I have been caught before and been really stuck, requiring recovery.
I would feel more confident going down them, if it was already on my gps, albeit marked as unconfirmed road, but better than nothing.

[Borgie]

Could we use GE as the basic source over laid with its roads, as a basis for creating a map for our routes?, of course these would have to be verified by GPS.

I live in an area where there is many new estates and roads, to be honest it would cost me a fortune to travel everyone. at the moment some of these new roads would save my gas, as they are shorter than the GPS maps, and I am reluctant to travel down a new road when I see it on the road, as I have been caught before and been really stuck, requiring recovery.
I would feel more confident going down them, if it was already on my gps, albeit marked as unconfirmed road, but better than nothing.

Yes. After tracing you can upload them here http://roadguide.ph/forums/showthread.php?t=3260 . This is an example of a traced contribution http://roadguide.ph/forums/showpost....08&postcount=4

You can also trace polygons, please refer to this thread http://roadguide.ph/forums/showthread.php?t=3261

HTH