Large driveway, patio or garden sundial

This is a design for analemmatic sundials, large or small, with elliptical dials.  The one I made with my son is twelve feet across, drawn in sidewalk chalk on a level part of our driveway, and you check the time by standing in the spot corresponding to the date and seeing where the middle of your ow shadow falls.  You can make a permanent one by first drawing in chalk and then painting over it (but we are renting the house).  

Drawing these is fun, and makes a good science education project for small or large kids (one's own, or a class at school).  It should take a little over an hour to do the basic measurements and drawing, more if one wants it to be more decorative.  Depending on the size and the features of your location, you may need up to two people's help with drawing the ellipse, though I will also say a little about how you can make it without drawing an ellipse.

Analemmatic sundials have a vertical gnomon (the pointer that makes a shadow) that is placed in a different location depending on the date, because the sun's position in the sky differs from month to month.  They are often made with the user acting as the gnomon, and the user's shadow showing the time.  The design is elliptical in shape and needs to have its dimensions and layout carefully customized for your latitude, longitude and timezone.  The design does not work well for latitudes within ten degrees of the equator.

Most of my time on the project was spent writing a sundial generator script to compute the dimensions and layout for the sundial for a given latitude, longitude and timezone.  But you don't have to do that.  You can now just go to my Analemmatic Sundial Generator website, input your location data, and the generator will automatically produce a PDF file you can print out that has all of the dimensions you need to measure out and draw the sundial.  And if you want to make a small sundial (e.g., on a piece of wood or metal, with holes drilled for the movable gnomon), you can just trace the drawing from the PDF file.  The script is open source, so you can download it and modify it for your own purposes.

The theory of analemmatic sundials is nicely explained here in mathematical detail (I got most of the formulas for my generator from there).  You can also see the Wikipedia article for photos that might inspire you.

In the following instructions, I will assume that like me you will make the design in chalk on a large, level paved area.  Please make sure you have the legal right to draw in chalk where you are doing this.  This would be a great project on a college campus if there is an area where chalk drawing is allowed (or you can get permission from the administration), or else you can do it on your own driveway or a walkway if it's level.  If you do it at home, you can make it permanent by painting over it.  

Many variations are possible.  Chalk on concrete or asphalt is not the only way.  You can draw it with a stick in soil or sand or snow, for a very impermanent one.  Or you could also lay it out on grass (see the Step 4 variations), and then put flagstones--or sticks, for a temporary version while camping--where the hours are, or you could just make a small one out of wood or metal.

Tools needed:

• measuring tape and/or yardstick (both is better)
• unstretchy string (my driveway sundial needed about 22 feet of string)
• something with a right angle (e.g., a piece of paper, a box, a carpenter's square, etc.)
• chalk (I recommend ordinary board chalk for the initial drawing, and then going over with either paint or sidewalk chalk for final lines)
• enough flat and level space for the sundial (12 feet across is good for a child-sized one; proportionately more for adults; less if you want to hold a stick in place as a gnomon)
• two pencils / screwdrivers / pieces of dowel / etc.
• computer with Internet access and PDF viewer
• printer and paper (you could also take a laptop outside without printing, but you'll have a hard time keeping it free from chalk dust)
• optional: paint
• optional: magnetic compass

As a warmup, you might consider doing this even simpler non-analemmatic paper sundial.

Step 1 Running the sundial generator

You will need to have the following information:

• your zip code (if you're in the US) or latitude/longitude (this site may help)
• your timezone
• whether your location has daylight savings time (time change between winter and summer time).

You will also need to decide how wide your sundial is going to be (mine is about 12 feet or 360cm;  it's probably fine for someone a bit more than five feet tall), and what you want to do about daylight savings time.  If your location has daylight savings, you have two main choices: label the clock with winter time and then add an hour to what the clock shows during summer time, or label the clock with summer time and then subtract an hour during winter time.  If you are making a temporary installation, you can also just use the current daylight setting, and not worry about what will happen after the time change.

Now go to my script's website analemmatic.sf.net.  Start by filling out your desired actual sundial width, and select the units.  The units you choose will determine the units in which all your dimensions will be calculated.  If you choose millimeters, centimeters or inches, the script will give you all your dimensions in these units.  (Note: If you chose inches, and your sundial is not too large, your dimensions will include fractional parts, e.g., 2 7/8".  Of course, decimal is used with metric units.)  If you choose feet, the script will give you all your dimensions in feet and inches (and fractional parts of inches if the sundial is not too large).

Then fill out your zip code or latitude/longitude, choose your timezone, and select what you want to do about daylight savings.

I recommend you leave the "Include (x,y) coordinates" option unchecked.  The one exception is if you are unable to draw the ellipse on your surface (e.g., you're putting down flagstones on grass) and want to use an alternate method that does not involve drawing an ellipse, but measuring out hour marks with two coordinates (see the second half of Step 4).  Please leave the "dimensions and instructions" option checked, unless you just want to print out a scale drawing of the final sundial with no dimensions (which might be fun if you want a paper sundial).

Click on "Submit" to generate your sundial PDF.  If you are having trouble viewing it, you may need to first download a PDF viewer here and/or try a different browser.  Print out the file.  You will now have pages corresponding to steps 2-6 in this Instructable. 

Note 1: Although I will give excruciating detail of the steps, you might just find the PDF file self-explanatory. 

Note 2: The instructions will include images of the PDF file for my location.  Yours will look somewhat different (especially different if you're in the southern hemisphere).  Do not use my images--run the generator for your own.  The exact shape ("eccentricity") of the ellipse matters crucially for this design of sundial.

Comments

[adrianvandenbergen]

Best Web-Site for Sun-Dial Construction yet.

Picture of three Floral Sundials:

One created for The Moonambel Easter Arts Festival

One created by the students and staff at Moonambel Primary School/

One of created at Gwynnyth Vineyard in the Victorian Pyrenees, which doubles as a mini-golf green.

[arpruss]

Very nice! I suppose the Easter Arts Festival one is set for one date, namely Easter of that year?

Did you make these?

[arpruss]

If you made one of these, please post a photo. I'll give a year of Instructables Pro membership to the best looking one (in my subjective judgment) posted between now and the end of September 25 Central Time (this is not open to Quebec users, so if you're in Quebec, feel free to post photos, but say that you're in Quebec--being Canadian (expatriate), I don't want to break the law of la belle province).

[jcoffin1]

I forgot to add, since my driveway does not see sunlight until almost 12pm, I intentionally left off the A.M. hours =).

[jcoffin1]

The family really enjoyed the project very much and your Sundial Generator made for an accurate dial. If it was off at all, it was not due to computer instructions. I live in the southern part of DE, and am on EST, so my dial reflects an ellipse for that time zone.

Should someone ask of me, "Where in the world are you?" I can point them to this sundial :-). Well, at least until the rain comes and washes it away. May need to make a smaller more permanent one that is pocket sized or something.

I posted a few pics of our sundial which was drawn up from the instructions of your Sundial Generator. Thanks again for making this project available to the public. All times were accurate to my local time. In the third photo, my wife's shadow is visible to the local time here.

[guaps]

This is great! I am making a large picnic table for my backyard, and I have been trying to create a cool design for the table top. This is perfect! I'll put a few small holes for each month in the middle of the table and have a giant sundial. Thanks for the great idea!

[arpruss]

That's a cool idea, especially since an ellipse nicely fits a rectangular table.

If you align the boards east-west, it'll be easier to get everything drawn on the table. If you can post a picture here once you're done, that would be really great.

[guaps]

I enthusiastically explained to my wife the great idea of a sundial on the table last night. She just stared at me for a second then said, "why would you want to sit in the sun on a hot summer day? Aren't you building the table under the trees?" She's right.

Your idea and instructable are awesome. My idea failed - sundials don't work very well in the shade.

[arpruss]

Your wife has an excellent point!

Though you might check just how total the shade is. If it's not total shadow, you may be able to read the sundial just fine--see my photos, since our sundial is in partial shade.

[sam D]

Awesome! I would love to laser etch a piece of used plywood and mount it in my garden. A different stick/gnomon for each season.

Can I rotate it 180degrees given that I live Down Under? I assume so....

[arpruss]

If you want to make a plywood one, I suggest just making a fairly standard garden sundial with an angled gnomon--you can use the generator for my other sundial instructable as a pattern. This way, the gnomon doesn't need to be moved. The feature that the analemmatic gives you is the ability to have an upright gnomon--e.g., a standing person.

Anyway, if you do want to make it, just enter a southern latitude into the generator (either this one or the other one) and it should work.  Don't just rotate a northern one, as that probably won't get the time-zone adjustment right.

I spent some time trying to figure out how to get my analemmatic generator to work in the southern hemisphere.  I generated a printout for a location in Australia, and then used an astronomy app to predict where the sun would be at the sky, and used a compass to measure out where the shadow would fall, and it worked.  I don't think I did as thorough testing of my other generator for the southern hemisphere.

[arpruss]

I figured out a way of doing this on grass or dirt without the need for xy coordinates, even if you can't draw the ellipse--you use the loop of string as a virtual ellipse when measuring. I added this method to step 4.

[pepperheads]

This would be a great thing to with individual plants in a garden. Offset the plants for the place you stand, and stand beside it. I bet it would even work on a larger scale using trees for the time points. Wow!

[arpruss]

If you were a good gardener and your local growing conditions were predictable, for some of the months you could use plants that bloom precisely in those months. Then for half of the year the instruction would be to stand by the blooming flowers!

But if you used trees for the time points, you'd need a really tall gnomon, unless your trees are pretty close together.

[whiteoakart]

If you were a tall pointy hat you may look like a garden gnomon! And you'll have a nice hour hand shaped shadow.

[arpruss]

That's a nice solution for a school project where some kids are shorter than others. Cuter than my idea that they can just join their hands over their heads.

[zigojacko]

Excellent, didn't realise there was these readily available resources for calculating your sundial requirements, would love to give this project a go sometime, would be great fun.

We help a lot of people clean their driveway and I shall start recommending this project as an additional feature to add beside their driveways! :) Heh

[arpruss]

Thanks!

Well, this particular online resource didn't exist before I made it. :-) But there are plenty of other resources online.

Just make sure the driveway is level. There are ways of correcting for unlevel ground, but I haven't figured out how to do that. It would require measuring the direction of the slope and the slope angle (this can easily be done with an iPhone or Android phone, since they have accelerometers). If enough people ask for this added feature, I *might* consider adding it to the script. But the construction will become more complex, because the horizontal axis will no longer be exactly east-west aligned, so one will have to measure angles.

I'm now working on another script, this time for a horizontal paper craft sundial. Would be very simple, except that I want the gnomon to be more three-dimensional for stability.

[CatTrampoline]

Very nice job, except now I have no incentive to finish my sundial instructable. Gasworks Park in Seattle, Washington has a really cool sundial like this on top of Kite Hill. There is a 10-15 foot long mosaic that you stand on.

[arpruss]

Thanks!  Talking of Seattle, have you seen this?  Some of these sundials are really cool.

[CatTrampoline]

The Sundial Trail looks really neat. I remember the wall-mounted analemmatic sundial on the Physics & Astromony building at UW, by the Burke-Gilman trail. If I still lived up there I'd go look at the others. Now I am seriously bummed about being in Texas.

.

[arpruss]

Thanks! I'm going to have to try to persuade my kids' school to paint one somewhere.

[wilgubeast]

This is awesome! I had no idea that the resources were so readily available for sun-dialing. I added this to the All Subjects Teacher's guide, as it'd make an awesome resource for telling time, teaching Greek history, and telling dorky jokes (a requirement of all teachers.)

"Did you realize it was so easy to make a sundial?"

"Gnomon."

Thanks for sharing this awesome project!