GPS HDOP
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Category: General Forums
Forum Name: Tech Topics
Forum Description: IT - Computers, software, phones, ISP's....
URL: https://www.fishing.net.nz/forum/forum_posts.asp?TID=124250
Printed Date: 04 Feb 2026 at 7:44pm
Topic: GPS HDOP
Posted By: macka2012
Subject: GPS HDOP
Date Posted: 10 May 2017 at 10:57pm
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Firstly, keep responses simple. Does anyone have any conversions for accuracy of GPS for HDOP readings from 1 to 20? ie what would be the HDOP for a GPS that is accurate to 20m for 95% of the time? God only knows why this is not in a table or documented on the internet...
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Replies:
Posted By: Steps
Date Posted: 11 May 2017 at 8:44am
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Does anyone have any conversions for accuracy of GPS for HDOP readings from 1 to 20? Out of interest Why? End of the day for general joe public HDOP and VDOP conversions mean nothing. Not only that,and never had the interest to get my head around DOPs, but it is my understanding these numbers are not so much as meters of error, but sort of a complicated semi logarithmic measure of the possibility of what the error could be, and usually , often 2 to 3 times the actual error. Anyway as the subject will most proberly be of interest to many, this is what I have found messing around over the last few yrs.... What is important is how accurate in meters are you to that rock? To give some idea just how accurate some devices are... Smart phone...I can locate another phone within 10m radius in a big store like red shed, or 1 car par space, what side of the road it is travelling. Or find a burgler who has stolen my old smart phone, and has gone to ground in trees, next to a high fence and over grown garden...2m radius A older garmin car nuvi....in a multi story car park..nothing... in city CBD street 10m elseware, what side of the road the car is on down to 3m older Lowrance elite 5 feeding my way thru the rocks in scullies reef, 2 to 3 m.. most properly less, 1/2 of that. My 10+yrs old huminbird 3 to 10m. Much depends on buildings etc around you... but have found cloud cover trees have little on no effect on the more modern units above. The software that calculates the information and able to read both the USA and Russian satellites makes a huge difference. I have noticed this on smart phone updates, the app software updates on the phones and a couple firmware updates on the huminbird and lowrance. |
Posted By: macka2012
Date Posted: 11 May 2017 at 10:15am
| I am a volunteer in Coastguard and we had a question asked, is HDOP with a value of 4 more or less accurate than a fix that is accurate to 20m 95% of the time. Trying to work out what the ratio are for meterage / HDOP values. |
Posted By: Steps
Date Posted: 11 May 2017 at 10:44am
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s HDOP with a value of 4 more or less
accurate than a fix that is accurate to 20m 95% of the time. Trying to
work out what the ratio are for meterage / HDOP values. Like I say above, End of the day for general joe public HDOP and VDOP conversions mean nothing. Not only that,and never had the interest to get my head around DOPs, but it is my understanding these numbers are not so much as meters of error, but sort of a complicated semi logarithmic measure of the possibility of what the error could be, and usually , often 2 to 3 times the actual error. From memory, and vague ball park. 1 is for high end surveyors that measure down to mm. Around 1.5 /2 is sort of around 3m And 20 , if from memory is the top is more around the 50. Bottom line thu, from my own messing around, for general navigation / position use on the road, general marine and hunting any modern unit or smart phone or tab in the last 5yrs will drop u within a max of around 2 to 5m Subject to being in an under ground carpark in between CBD buildings. If someone asked that question in that manner then IO believe they dont really understand what HDOP actually is or means.. I dont, other than it is not a conversion thing like deg C to deg F or m to Ft With smart phone/ tabs one can load apps to give that info... thu still have to compare directly to a map. Many garmin car units one .. cant rem how it goes now.. press top left cnr screen for a given time and then off button combo stuff. Chances are boat gps unit have similar technician ways to getting to the adman / logs/ hidden settings side of things. |
Posted By: macka2012
Date Posted: 11 May 2017 at 11:20am
Thanks Steps, that answers my query. 
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