There's no mystery surrounding a home's market analysis. You look at your home's specs (location, living space, amenities, schools, condition, etc.), then use the online property tax and real estate listings to see what's sold in your area in the last 12 months.
Look for similar properties and trends -- like the same house selling for more in 3 separate sales in 2 years.
If you can find 3-4 properties that sold, that provides enough data to do a comparison.
If you've refinanced, check the appraisal used if there was one done.
You should compare that to median house price stats. The median single-family home price on Oahu has been 15%-20% less than what my house appraised at. But the city&county assessment has been more like 25% less than market appraisal.
If you do the comparisons, you'll know if the tax assessment is in the ballpark or not.
YMMV