Country > Philippines > Bohol > Tagbilaran
Date > 2025 > February
Activity > Learning | Wealth Building

Property Mapping

Sketch
Plan

Bohol

Siquijor

February 27, 2025

Plotting Sketch Plan to Google Maps

Location : Tagbilaran, Bohol, Philippines

Take 2
I tried before to plot a sketch map of a real estate property on Google Map by converting numbers on the sketch map to GPS coordinates but got nowhere. My impasse the last time was asking AI how to convert sketch plan to GPS coordinates. I could then use the coordinates to plot a real estate property in Google Map. I did take pictures of the property markers, but the built-in deviation from the exact coordinates did not make it reliable. I still had to view the sketch plan to ensure the shape was accurate...lots of work. There had to be a better system. With a looming project, I had to give it another go, using a different approach.

No more GPS Coordinates
This time, I asked AI to overlay a sketch plan on Google Map without even mentioning 'GPS coordinates'. AI responds:

Google Gemini

Georeferencing and Overlaying - This is the most accurate method. It involves assigning real-world coordinates (latitude and longitude) to points on the surveyor's sketch plan and requires software like QGIS (free and open-source), ArcGIS (commercial) and AutoCAD Map 3D (commercial). Once georeferenced, the sketch plan can be saved as a georeferenced image (e.g., GeoTIFF) or a KML/KMZ file. These files can then be overlaid onto Google Maps or Google Earth.

HOW
a. Identify known landmarks or reference points on the sketch plan that also exist on Google Maps (this is crucial because if the sketch plan doesn't have any, it's end of story).

b. Use georeferencing software to align the sketch plan with the Google Maps coordinates.

c. Export the georeferenced image or KML/KMZ file.

d. Import the file into Google Maps or Google Earth.
Manual Plotting Using Google My Maps - If the surveyor's sketch plan provides coordinates (latitude and longitude), you can manually plot the property boundaries on Google My Maps (I like this approach but will learn this at a future time. For this project, I will bypass the complex process and deal with the sketch map directly).

a. Drawing Tools: Google My Maps provides drawing tools that allow you to create polygons and lines to represent the property boundaries.

b. Limitations: This method is less accurate than georeferencing, especially if the sketch plan is not precisely to scale or if coordinates are not available.

ChatGPT: Overlaying the Sketch Plan on Google Maps
Frustrated with all the complexities, I ditched the GPS-coordinates approach and used the digitized sketch plan to layover on Google Maps. This is not a straight forward process. ChatGPT provided some solutions:

Using Google Earth Pro

Overlaying an image (a cut-out of the property area) on Google Maps is not possible. I had to use Google Earth Pro (free download), add the 'image overlay', convert as KMZ file, fragment the KMZ file (why? because Google Maps cannot show an image overlay even though it is already a KMZ file) and put the modified KMZ file back together again, open up Google Maps, import the modified KMZ file as a new layer. Details are as follows:

Cut out the property area using Photoshop - I opened up the digital sketch map on Photoshop, traced the boundary lines and cropped the area. I now have the shape of the property as a cut-out. Save the cut-out file.

cut out the property area using Photoshop

the cut-out of the property area using Photoshop

Find the general location of the property on Google Earth Pro - use landmarks (road, intersection, bridge, rivers). This will ease the overlaying of the cut-out

find the general location of the property on Google Maps

identifying the general location of the property on Google Earth Pro

Menu > Add > Image Overlay - on Google Earth Pro, Menu > Add > Image Overlay. The interface will show a dialogue box and the map will show markers with a "+" at the center.

the dialogue box and the map with green markers with + at the center

Overlay the cut-out image - on the dialoque box, go to the cut-out file, adjust transparency and name it. Do NOT click OK yet - do this when you have already sized the cut-out. The cut-out image will appear on the map...it might be too big or too small. Use the green markers to adjust the size and location, using the landmarks for guidance. Now you can click "OK"

cut-out image adjusted to the right size and location using established markers on the map - road, intersection, river, etc.

Saving the cut-out as a KMZ file - on the left panel, select the layer with the image overlay, right-click, Save Place as, then another dialogue box appears where you can save the overlay as a KMZ file. Normally, you can export this KMZ file into Google Maps but as an image overlay, you won't see the image in Google Maps because it does not support embedded images but it will support external images. You have to go through another complexity.
KMZ to Zip - on Windows Explorer (not on Google Earth Pro), rename the KMZ file to a zip file eg cutoff.kmz to cutoff.zip Unzip it and you should see a KMZ file AND an image file.

a) Upload the image file to an online server (your website, Google Drive, Google Site, etc.) and get the complete url, e.g. https://www.mysite.com/images/cutout.png

b) Open the KMZ file on Notepad. Where it says, "cutout.png", replace this with the full url "https://www.mysite.com/images/cutout.png" and save the kmz file (this kmz file no longer contains the image). Zip this file, so from cutout.kmz, it is now cutout.zip. Now, change the file extension to kmz, so the final file is renamed cutout.kmz
Import the modified KMZ file to Google Maps - Launch Google Maps and create a new layer. Select the new layer and on the 3 vertical dots to its right, name it and Import the new KMZ file. The image overlay should now show up on the map.

Despite meticulously doing all the above, the image overlay still did NOT show up...very frustrating !!!

Using Google Earth Web

You have to create a Project inside the Google Drive using Google Earth Web in order to share the file. By making the file 'shareable', you are allowed to embed the map into a webpage.

Open Google Earth Web - once open, on the top right, select Google Drive (not Local Device). On the left panel, click + New > New Project and the map interface shows up. Name the project and save it. On the top right, you now see the Share button active (not grayed out).

by opening a new project, the Google Earth Web interface shows up

Import KMZ file into the project - on the left panel, click + > Import KMZ into Project > Import from Drive or Upload from Device (choose where you filed the KMZ file). Once the KMZ file is selected and clicked OK, the image overlay shows up on the map

once the KMZ file is selected and clicked OK, the image overlay shows up on the map

Share - apart from 'Share' on the top right, you also have to 'Share' using the left panel. On the left panel, click the 3 vertical dots, Share > Share a Project you Own? > Continue. A new dialogue box shows up, General Access > Anyone with a Link (not Restricted) > Copy Link > Done. Paste the link to a browser url and you should see the map with image overlay. To embed the map on a webpage or to Google Site, use the IFRAME tag and insert the Link_Url.

The link worked on the browser - the map showed up with the image overlay.

the link worked on Google Chrome - map and image overlay

Embedding Failed - But when embedding the code on a website, the map didn't show up. According to ChatGPT, "Google Earth Web links cannot be embedded directly in an iframe". Sigh...really frustrating!

Google Earth Web (with overlay)

Using standard HTML embed Tag - still, nothing showed up

Using Google Maps API - first, I don't know how to program. 2nd, when I tried to get a Google Maps API, they asked for payment information - my GCash info wasn't acceptable to them. So, that was it.

Embedded Google Earth Map

AHA Moment!
Frustrated from all the foregoing, I went to sleep feeling defeated. It was then when I received an Aha Moment - on Google Earth, I already have the image overlay. What if I put a 'marker' on every corner of that image as they represent where the concrete property markers are? That marker is georeferenced and can be exported as a KMZ file. I can then open Google Maps and import that KMZ file. Since the content are just Google-generated landmarks and not an image overlay, it should show up. True enough, the landmarks showed up. From there, I simply connected the markers using a polygon tool - that area represents the lot area coverage. And it all worked!

Selling the Land
I usually do the mapping for a fee - no commission when it gets sold. This way, I get the quick cash and not have to go through the series of follow-throughs with the owner...or even go to litigation in case of snags. I don't need the mess.

But why not? If I already have the map, I can clone it with my tweaks and use it independently for a commission when the land gets sold. If I can have a written agreement (not necessarily a contract but even on Messenger), I would have something to hold on to.

Filtering the Buyers
If I do try to sell the property, I asked ChatGPT how I could screen the serious buyers. There are serious buyers but there are more "just looking" inquiries and those who'll waste my time. Solution?

Serious Buyers Only - on the webpage, add the line, "Serious inquiries only. Proof of funds or pre-approval required before site visits."
"What do you plan to do with the land?" - a real buyer should have a clear purpose
"Do you have financing or cash available?" - ask for proof of funds (bank statement, loan pre-approval, or letter from their financial institution)
"Have you purchased land before?" - experienced buyers are usually more serious

*** If they hesitate on the answers or not transparent, it's a red flag.

Request a letter of intent (LOI) - ask before detailed negotiations
Video call - for Site Visits, schedule a phone or video call to confirm interest
Refundable deposit - charge a refundable deposit for site visits (this weeds out casual lookers)

Ending Thoughts
After trying out so many approaches and not one working at the end of all my trouble was heartbreaking. I can't count how times an Aha Moment saved the day for me. But in fairness, this Aha Moment would not have come had I not labored over the many approaches I took. If I close this article with a take-away, it's "Do the due-diligence and the heavens might sympatize."

Another take-away is to follow through an idea. After creating a map for a client, why not also offer to sell the property for a commission? Just ensure there is a written understanding so it's not just 'talk'.

--- Gigit (TheLoneRider)
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