The difference seems rather a lot for what is basically a rounding error in the way that the surface of the earth is projected on to a flat map,
several sources say the difference would generally be less than 2 degrees, on my topo map in NSW it is 0.6 degrees,
it looks more like the magnitude of the difference between TN and magnetic north for most of Oz unless you are in WA.
I wonder if your lot was surveyed using magnetic bearings. Around these parts the current maps are about 11 degrees difference between TN and MN - it changes slowly over time as the magnetic poles move. However all the old fence lines are about 9 degrees different from true bearings. My supposition is they were surveyed on magnetic bearings as this was the magnetic declination at the time. I can’t find any description of the historical surveying that would confirm or deny this.
Without getting too personal about where are you? A nearby town or map sheet name would do.
I checked what my surveyor wrote, which needed some careful reading to answer your question. Sorry for the long answer.
It appears you are quite right. The surveyor specifically said that what he called Survey North on my title plan was 8.5º east of True North, and he said it was not exactly the same as Magnetic North currently. (Maybe it was once since magnetic moves each year a small amount.)
But interpreting what he said about grid convergence, there is another north obviously which is Grid North, which does vary from True North due to map convergence issues, and is probably what as you said is used for standard topo maps. I was too busy re-thinking my solar to notice this at the time as it did not affect me.
He did not say the exact difference between Grid North and True North except that it was not much. It sounds like you know more about this than me, so if there are different topo map grids used in different places or for different scales or countries, or if they are all the same, I’ll leave that to someone else to look into.
All I know, now that my house is built, is to know it is misaligned to 28.5E due to no-one including me, the draftsman or the builder understanding the True North point, but the panels are now True North 0º which is what I wanted!
I’m on the East coast of OZ roughly near Gympie. The main subdivision I live in was done about 15 years ago so the master site plan dates from then, but the original area and the roads would have been surveyed much earlier. It was farmland from at least as far back as 1915 when a little town started up nearby, but the area was farmed earlier than that. My block was further divided off a bigger one at time of purchase in 2015.
So I have no concrete idea how the Survey North on the plan came to be so far different. But I guess if it can happen to me, it can happen to anyone so maybe it can still be relevant to other readers to check before building, or before installing solar. I only cottoned on when I saw a solar app which showed True North over a satellite photo of the land.
It’s not uncommon for some sites and common in civil construction to assign an arbitrary North South line.
EG local north, plan north, plant north.
The arbitrary line may align to a local feature, site characteristic, or construction requirements.
Prior to affordable highly accurate GPS based survey, finding survey points accurately was very challenging.
It’s still common today to layout large sites that have complex civil construction (eg oil terminal, sewage treatment plant, power station) with a nominal plant north line. It serves as a single base line from which all design is laid out. On site the same base line is used as a reference to ensure the set out of all works is accurate. I’ve seen ‘plant north’ drawings that point more south than north, after the works for the site have been relocated for a better alignment with topography.
Given the age of the site it is possible Survey North was defined for the sub-division based on some pre-exiting site detail. It may become obvious (or not) when you look at the details of old boundaries and roads.
Miscommunication and misunderstanding is not uncommon.
Our house was designed to face east, it was relocated and intended to face west, but then placed facing magnetic south. I know how you must feel. We have shady verandahs facing every direction but west!
Yes that seems about right, the latest topo map says magnetic declination is 10.5 degrees and grid convergence (GN to TN) is negligible.
To go back to the original issue, the difference between GN and TN is very unlikely to make any significant difference to the performance of your solar panels. The difference between MN and TN varies (now) from about 11 degrees on the east coast down to close to zero in WA. This might make a small difference but not much.
For example several solar calculation sites show graphs for the difference in performance at various orientations. Ignoring the very real question of what time of day do you want your power, typical reduction of efficiency at either east or west orientation varies somewhat but is about 85% of north orientation. So 0-11 degrees difference (compared to 90 degrees) will not be a big difference in output.
So let us try to organise panels to face TN or to take into account when we need power if not at TN. But if you are a few degrees off don’t sweat.
She said changes to the solar tariff in Western Australia made installing home batteries more attractive.
“The new system is now going to be paying 3 cents during the day. And then from 3 o’clock to 9 o’clock they’ll pay you 10 cents for whatever you export out,” said Ms Barnett.
It does not look that attractive.
There are various estimates for the cost of home battery systems. Between 30c and 40c per kWh of lifetime stored energy averaged over ten years. Based on the purchased installed value, no DCF. A long way short of break even.
With the most expensive generation during the evening peaks, it would seem more logical to encourage battery storage soaking up peak day time output and paying a premium to owners for helping to meet peak evening loads. At rates comparable to the real cost to the network of gas powered peak generation.
Commercial realities of generation, investment and Government still lead.
